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–+ servings

Broccoli Fish Bake

Dinner
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.
Broccoli Fish Bake recipe
Prep Time 20 minutes
Cook Time 35 minutes
Total Time 55 minutes
Servings 4

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

Equipment

Instructions

  1. 1. Prep your ingredients
    Preheat your oven to 190°C (170°C fan). Butter your ovenproof dish generously. Cut the fish into large chunks, about 4cm pieces. You don't want them too small or they'll fall apart. Season with salt, pepper, and a squeeze of lemon. Cut the broccoli into florets, keeping them roughly the same size so they cook evenly. Slice your potatoes thinly, about 3mm thick. A mandoline makes this easier, but a sharp knife works too.
  2. 2. Blanch the broccoli and potatoes
    Bring a large pot of salted water to the boil. Blanch the potato slices for 3-4 minutes until they're just starting to soften but not cooked through. Scoop them out with a slotted spoon and set aside. Use the same water to blanch the broccoli for 2-3 minutes, it should still have a bit of bite. Drain well. This step means everything cooks evenly in the oven and you're not left with crunchy potatoes or mushy broccoli.
  3. 3. Make the béchamel
    Melt the butter in a saucepan over medium heat. Add the flour and whisk constantly for about a minute, this cooks out the raw flour taste. Gradually add the milk, whisking as you go to avoid lumps. Keep whisking until the sauce thickens enough to coat the back of a spoon, takes about 5-7 minutes. Add the mustard, nutmeg, and season with salt and white pepper. The sauce should be creamy but pourable, not thick like wallpaper paste.
  4. 4. Layer the casserole
    Start with a layer of potato slices on the bottom of your buttered dish, slightly overlapping. Add half the fish chunks, then half the broccoli florets. Pour over about a third of the béchamel sauce. Repeat with another layer of potatoes, the remaining fish, remaining broccoli, and another third of the sauce. Finish with any remaining potatoes on top, then pour over the last of the sauce, making sure everything's covered.
  5. 5. Prepare the breadcrumb topping
    Mix the breadcrumbs with the melted butter in a small bowl until all the crumbs are coated. This is what gives you that golden, crispy top. Scatter the buttered breadcrumbs evenly over the entire surface of the gratin. Don't press them down, just let them sit on top loosely.
  6. 6. Bake
    Bake for 30-35 minutes until the breadcrumbs are properly golden and crispy, and the sauce is bubbling around the edges. The fish should be cooked through and flake easily with a fork. If the breadcrumbs are browning too quickly, cover loosely with foil for the first 20 minutes, then remove it to let the top crisp up.
  7. 7. Rest and serve
    Let it sit for 5-10 minutes before serving. This gives the sauce time to settle and makes it easier to portion out without it collapsing into a mess on the plate. Serve with a simple green salad or some crusty bread to mop up the sauce.

Notes

  • Any firm white fish works here, avoid oily fish like salmon or mackerel, which don't suit the creamy sauce.
  • Make your own breadcrumbs from stale bread if you can. They're better than shop-bought and give you a more irregular, crispy texture.
  • You can swap the broccoli for cauliflower, or use a mix of both.
  • Add a handful of frozen peas in with the broccoli if you want extra veg.
  • This keeps in the fridge for 2 days. Reheat covered with foil at 180°C for 20 minutes.
  • For a richer version, replace 100ml of the milk with single cream.