Broccoli Fish Bake
Dinner
November 10, 2025
Broccoli Fish Bake
Flaky white fish baked with broccoli and potatoes in creamy béchamel, finished with golden, buttery breadcrumbs. This is French gratin technique at its best, layers of good ingredients cooked slowly until everything melds together and the top goes crispy.
November 10, 2025
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I’ll admit it: I am a true béchamel person. Give me that silky white sauce over almost anything and I’m happy, so it’s no surprise this broccoli fish bake has become a regular in our house. It’s the dish I start craving the moment summer tips over into those first proper chilly evenings, when you want something warm, creamy and comforting without much effort.
Béchamel is one of the French mother sauces, and to me it’s pure comfort food. I use it on a croque madame, in a salmon lasagna, and here it does the same generous thing: it brings a richness that makes you want to scrape the dish clean. And the best part is how little this asks of you. Layer, pour, scatter breadcrumbs, bake. Dinner for the whole family, no stress.
Table of Contents
Where broccoli fish bake comes from
In France this is a gratin de poisson, a fish gratin, and the word gratin is the key to the whole thing. It comes from gratter, to scrape, and originally meant the browned, crusted bits scraped from the bottom and sides of the baking dish, the part everyone fights over. Over time the name came to mean the whole dish.
Here the crust is buttered breadcrumbs with parsley, baked until crisp. It might surprise you but there is no cheese in this baked cod recipe. Traditional French baked fish gratins stick to béchamel and breadcrumbs rather than a cheesy top, because the béchamel gives the creamy richness, the breadcrumbs give the crunch, which is for fish more satisfying than an ingredient that covers the flavours. A heavy layer of melted cheese would take over a delicate piece of white fish.
Ingredients
- White fish — cod, haddock or pollock. You want a firm white fish that holds together through baking and stays in flakes rather than dissolving into the sauce.
- Broccoli — for colour and texture. Blanched only briefly so it keeps some bite, since it finishes cooking in the oven and over-blanched broccoli turns grey and soft.
- Waxy potatoes — they hold their shape, stretch the fish further, and make the dish a complete meal.
- Butter, flour and milk — the béchamel. Made a little thicker than you’d want for pasta, so it coats the layers and holds them together.
- Dijon mustard and nutmeg — a teaspoon of mustard for a gentle savoury lift, and nutmeg, the classic béchamel seasoning that makes the sauce taste finished rather than flat.
- Breadcrumbs — tossed with melted butter for the crisp golden top. Homemade from stale bread are better than shop-bought, giving a more irregular, crunchy crust.
- Lemon — a squeeze over the fish, which brightens it against all that cream.
How to make broccoli fish bake
1. Prep everything first
Heat the oven to 190°C (170°C fan) and butter the dish. Cut the fish into large 4cm chunks, so they hold together rather than falling apart, and season with salt, pepper and a squeeze of lemon. Cut the broccoli into even florets and slice the potatoes thinly, about 3mm, on a mandoline if you have one.
2. Blanch the potatoes and broccoli
Bring a large pan of salted water to the boil. Blanch the potato slices for 3 to 4 minutes, until just starting to soften, and lift them out. In the same water, blanch the broccoli for 2 to 3 minutes, so it keeps some bite, then drain well. This step is what stops you ending up with crunchy potato and mushy broccoli from the same bake.
3. Make the béchamel
It should be creamy but pourable, not stiff.
4. Layer the gratin
Start with a layer of potato slices, slightly overlapping, then half the fish and half the broccoli, and a third of the béchamel. Repeat with another layer of potato, the rest of the fish and broccoli, and another third of the sauce. Finish with the last potatoes and the final third of béchamel, making sure everything is covered.
5. Add the breadcrumb top
Toss the breadcrumbs with the melted butter until evenly coated, then scatter them loosely over the whole surface. Don’t press them down, since loose crumbs crisp better. This is what gives you the golden, crunchy top that makes it a gratin.
6. Bake until golden and cooked through
Bake for 30 to 35 minutes, until the breadcrumbs are deep golden, the sauce is bubbling at the edges, and the fish flakes easily with a fork. Check the fish is cooked through at the centre, since it goes in raw and the béchamel insulates it. If the top browns too fast, cover loosely with foil for the first 20 minutes, then uncover to crisp up.
7. Rest, then serve
Let it sit 5 to 10 minutes before serving, which lets the sauce settle so it portions cleanly rather than sliding across the plate. Serve with a simple green salad or crusty bread to mop up the sauce.
Tools for this recipe
Check out my favorite kitchen essentials and cookware!
- Use a deep baking dish with high enough sides that the béchamel doesn’t bubble over, and heavy enough to hold heat steady so the crumbs brown evenly without catching.
- Use a whisk for the béchamel, since a spoon won’t clear lumps once they form.
- Use a saucepan with a heavy base so the sauce doesn’t catch while it thickens.
- Use a mandoline for even 3mm potato slices, which cook at the same rate. A sharp knife works too.
Tips for success
- Make the béchamel a little thick: for fish you want it thicker than pasta sauce, so it coats the layers and binds them rather than running to the bottom of the dish and leaving the top dry.
- Don’t over-blanch the broccoli: two to three minutes, still with bite. It finishes in the oven, and broccoli blanched soft turns to grey mush under the sauce.
- Cut the fish into big chunks: 4cm pieces hold together and stay in flakes. Small pieces disintegrate into the béchamel and you lose the fish entirely.
- Check the fish is cooked at the centre: it bakes from raw under an insulating layer of sauce, so make sure the thickest chunks flake cleanly before serving.
- Dry the blanched vegetables well: excess water thins the béchamel and makes the bake watery, so drain the potatoes and broccoli properly before layering.
- Use stale bread for the crumbs: homemade crumbs from day-old bread give an irregular, crunchy top that shop-bought fine crumbs can’t match.
- Let it rest before serving: five to ten minutes lets everything set so it holds its shape on the plate instead of collapsing.
How to store it
- In the fridge: Keeps 2 days covered. The flavours settle and are arguably better the next day, though the crumb topping softens. Reheat covered with foil at 180°C for about 20 minutes, until hot through.
- Making ahead: You can assemble this dish, minus the breadcrumbs, and keep it covered in the fridge for a few hours before baking. Add the buttered crumbs just before it goes in, so they stay crisp.
- In the freezer: Not ideal. The béchamel can split slightly and the fish and potato soften on thawing. If you must, freeze it before baking, then thaw fully and bake fresh.
Variations
- With cauliflower: swap the broccoli for cauliflower, or use a mix of both. Cauliflower and béchamel is a classic French pairing in its own right.
- With peas: a handful of frozen peas tucked in with the broccoli, for extra greens and a bit of sweetness.
- Richer: replace 100ml of the milk with single cream for a more luxurious béchamel, good for a special occasion.
- With smoked fish: use some smoked haddock alongside the cod for a deeper, smokier flavour, which is very good with the creamy sauce.
- With leeks: a layer of softened leeks between the fish and sauce, since leeks and white fish are a natural match.
- With prawns: scatter a few raw prawns through the layers along with the fish, for a mixed seafood gratin.
FAQ
What fish is best for a fish bake?
A firm white fish that holds together through baking: cod, haddock or pollock. Avoid oily fish like salmon or mackerel, which don’t suit the creamy béchamel.
Do you cook the fish before baking?
No, the fish goes in raw and cooks through in the oven. Cut it into large 4cm chunks so it holds together, and check the thickest pieces flake cleanly before serving, since the sauce insulates them.
Why don’t you put cheese on a French fish gratin?
Traditionally a fish gratin uses béchamel and breadcrumbs rather than cheese, so the delicate fish flavour comes through. A heavy cheese topping would overpower it. The crisp top here comes from buttered breadcrumbs.
Can you make broccoli fish bake ahead of time?
Yes. Assemble it without the breadcrumbs and refrigerate for a few hours, then add the buttered crumbs and bake. It also keeps 2 days cooked, reheated covered at 180°C.
How do you stop a fish bake being watery?
Blanch the vegetables only briefly and drain them well, and make the béchamel on the thick side. Excess water from the vegetables and a thin sauce are the usual causes of a watery bake.
Prep Time 20 minutes 
Cook Time 35 minutes 
Total Time 55 minutes 
Servings 4Description
Flaky white fish baked with broccoli and potatoes in creamy béchamel, finished with golden, buttery breadcrumbs. This is French gratin technique at its best, layers of good ingredients cooked slowly until everything melds together and the top goes crispy.
Ingredients
For the casserole
- 500 gr cod haddock, or pollock work well too
- 300 gr broccoli
- 2 waxy firm potatoes about 300g
- 50 gr breadcrumbs
- 30 gr unsalted butter
- squeeze lemon juice
For the béchamel
- 40 gr unsalted butter
- 40 gr plain flour
- 500 ml whole milk
- 1 tsp mustard Dijon
- 1 pinch nutmeg
- salt and black pepper
Instructions
1. Prep
- Preheat the oven to 190°C (170°C fan) and butter the dish. Cut the fish into 4cm chunks and season with salt, pepper and lemon. Cut the broccoli into even florets and slice the potatoes 3mm thick.
2. Blanch
- Boil a large pan of salted water. Blanch the potato slices 3–4 minutes until just softening, lift out. Blanch the broccoli 2–3 minutes, keeping some bite, and drain well.
3. Make the béchamel
- Melt the butter, whisk in the flour and cook 1 minute. Add the milk gradually, whisking, until it coats the back of a spoon, 5–7 minutes. Stir in the mustard, nutmeg, salt and white pepper. Keep it creamy but pourable.
4. Layer
- Potato slices on the bottom, then half the fish, half the broccoli, a third of the sauce. Repeat with potato, the rest of the fish and broccoli, another third of sauce. Top with remaining potato and the last of the sauce, covering everything.
5. Prepare the breadcrumb topping
- Toss the breadcrumbs with the melted butter and scatter loosely over the surface. Don't press down.
6. Bake
- Bake 30–35 minutes, until the crumbs are golden, the sauce bubbling, and the fish flakes easily. Check the centre is cooked through. Cover with foil for the first 20 minutes if browning too fast.
7. Rest and serve
- Let it sit 5–10 minutes before serving, with a green salad or crusty bread.
Notes
- Any firm white fish works. Avoid oily fish like salmon or mackerel.
- Homemade breadcrumbs from stale bread give a better, crunchier top.
- Swap the broccoli for cauliflower, or use both. Add peas for extra veg.
- Keeps 2 days in the fridge; reheat covered at 180°C for 20 minutes.
- For a richer version, replace 100ml milk with single cream.
Share your feedback and spread the love!
If you try this recipe, I’d love to hear how it turns out! Leave a ★★★★★ rating and your thoughts in the comments, it helps fellow French foodies discover this recipe too. Snap a photo and tag @obviously.french on Instagram. Come talk about it in our Facebook group. And don’t forget to save this recipe to Pinterest so you’ll always have it handy for your next French-inspired meal!
