Gratin de poisson – fish casserole with vegetables and cheese Recipe
A French casserole with pieces of white fish, vegetables and a delicate sauce under a cheesy crust is a convenient dish for a family dinner. It’s a bit like a cross between Greek-style fish and a pasta bake, just without the pasta. In France, such gratins are often made from leftover cooked fish from the previous day so that nothing goes to waste.
This gratin combines tender white fish, creamy sauce and soft potatoes under a golden cheese crust, making it both comforting and elegant. It’s also a great way to use up leftover cooked fish in a new, family-friendly dish.
Chef's tips
Slice the potatoes as evenly and thinly as possible so they cook through at the same time. If you’re using very firm potatoes, you can briefly parboil the slices for a few minutes before layering. Taste the sauce and season it well – it should be slightly more seasoned than you think, as the potatoes will absorb some of the flavor.
How to serve
Serve the gratin hot, straight from the oven, with a crisp green salad or steamed green beans. A wedge of lemon on the side will brighten the flavors, and fresh herbs like parsley or chives sprinkled on top just before serving add freshness.
Ingredients
- white fish fillet e.g. cod, pollock, hake - 500 g
- potatoes cut into thin slices - 400 g
- carrot cut into thin slices - 2 piece
- leek white part, cut into half-moons - 1 piece
- butter - 2 tablespoon
- wheat flour - 1.5 tablespoon
- milk - 300 ml
- cream 18–30%, optional - 50 ml
- yellow cheese grated, well-melting - 120 g
- lemon juice - 1 tablespoon
- thyme dried leaves or fresh - 1 teaspoon
- salt to taste
- pepper to taste
- oil for greasing the dish - 1 tablespoon
Preparation
- Preheat the oven to 190°C (top and bottom heat). Lightly grease a baking dish of about 20×30 cm with oil.
- Peel the potatoes and cut them into thin slices (about 3 mm). Peel the carrot and cut into thin slices. Clean the leek and cut into half-moons.
- Check the fish fillet for bones and remove them, then cut the fish into larger pieces (about 3–4 cm). Drizzle with lemon juice, sprinkle with salt, pepper and half of the thyme.
- Melt 1 tablespoon of butter in a pan over medium heat. Add the leek and carrot, a pinch of salt and fry for 5–7 minutes, stirring, until the vegetables soften slightly.
- Arrange half of the potato slices on the bottom of the baking dish, slightly overlapping. Season lightly with salt and pepper.
- Spread the sautéed vegetables over the potatoes, then place the pieces of fish on top. Cover with the remaining potatoes and season lightly again with salt and pepper.
- Prepare the sauce: melt the remaining 1 tablespoon of butter in a saucepan. Add the flour and stir for 1–2 minutes over low heat until a smooth paste forms, but do not let it brown.
- Gradually pour in the milk, whisking constantly so that no lumps form. Cook for 3–4 minutes until the sauce thickens to the consistency of a thin pudding. Add the cream (if using), the remaining thyme, a pinch of salt and pepper. Remove from the heat.
- Pour the sauce evenly over the casserole, moving the dish slightly so the sauce seeps between the layers.
- Sprinkle the top with grated cheese.
- Cover the dish with aluminum foil and bake for 20 minutes. Then remove the foil and bake for another 10–15 minutes, until the potatoes are tender and the cheese on top is golden and slightly crispy.
- After removing from the oven, let the casserole rest for 5–10 minutes so it sets slightly and is easier to slice.
Storage
No storage information available for this dish.
This dish is inspired by classic French fish gratins that turn simple ingredients into something cozy and satisfying. It’s perfect for weekends when you want a complete meal from one dish and minimal washing up afterwards.
