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Fish, Northern, Eastern and Western France

Gratinéed fish shell scallops with mashed potatoes

Gratinéed fish shell scallops with mashed potatoes is a traditional dish made with cod, mushrooms and Mornay sauce, baked until golden and served with homemade mashed potatoes. It takes 55 minutes for 4 people, has a moderate difficulty level, and costs about €3.90 per person. The key to success is a smooth bechamel and a well browned top under the broiler.

Tonight, fish shells filled with white fish and mushrooms in Mornay sauce, gratinéed, with homemade mashed potatoes.

Gratinéed fish shell scallops with mashed potatoes
Total time
55 min
Difficulty
Medium
Cost per person
€3.90
Calories per person
750 kcalcalculated by Kiloach, your weight coach
Season
Fall, Winter
The kids
They generally like it

Under the golden layer of melted Swiss cheese, flaked white fish meets mushrooms in a creamy Mornay sauce, rich but never heavy. A pinch of nutmeg quietly rounds out the flavor, and the contrast between the crisp gratin top and the soft mashed potatoes is what makes this dish work. It's generous and comforting, the kind of meal that smells like a family kitchen on a slow afternoon.

This is the sort of recipe to make on a fall or winter Sunday, when you have time to get the bechamel and the mashed potatoes just right. Kids usually like the mild, tender fish hiding under the melted cheese. Mon Chou suggests this dish when you want to cook simply with white fish, without reaching for anything complicated.

The ingredients

4 people

Fish counter

  • White fish fillets 600 g

Fruits and vegetables

  • White mushrooms 200 g
  • Potatoes 1 kg

Dairy

  • Butter 100 g
  • Milk 50 cl
  • Grated Swiss cheese 100 g

Pantry

  • Flouroften in the pantry 40 g
  • Nutmegoften in the pantry 1 pinch
  • Saltoften in the pantry 1 pinch
  • Pepperoften in the pantry 1 pinch

Allergens Fish, Lactose, Gluten

The step by step recipe

  1. Poach the fish in simmering salted water, then flake it. 8 min

    Run your finger over the flesh to check for any leftover bones.

  2. Melt half the butter, stir in the flour, then add the milk little by little to make a bechamel, mix in half the Swiss cheese, the nutmeg, salt and pepper.

    Whisk constantly over low heat to avoid lumps.

  3. Pan fry the sliced mushrooms and mix them into the fish and sauce. 5 min

    Let them cook off their liquid first before adding the butter.

  4. Fill the shells, sprinkle with the remaining Swiss cheese and broil at 220°C. 15 min

    Switch to broiler mode for the last five minutes for a nicely browned top.

  5. Make the mashed potatoes with the cooked potatoes, the remaining butter and hot milk, then serve with the shells. 20 min

    Mash the potatoes with a potato masher, never a blender.

Our tips to get it right

  • Pick a fresh white fish fillet that isn't too watery, it will flake more cleanly into the sauce.
  • Drain the poached fish well before folding it into the bechamel, otherwise the filling turns runny.
  • Serve the shells right out of the oven, the gratin top loses its crispness as it cools.

The variations

  • Swap the cod for hake or pollock, two white fish that flake just as well.
  • For a fish free version, double the mushrooms and stir in cooked spinach with the Mornay sauce.
  • For a faster version with hungry kids, use instant mashed potatoes and focus your time on the gratin.

What to serve it with

  • A sharply dressed green salad
  • Grilled country bread
  • A glass of dry cider

Storage

The gratinéed shells keep for 2 days in the refrigerator in a sealed container. They don't freeze well because of the mashed potatoes and bechamel. Reheat them in the oven so the top crisps up again.

Questions about this dish

Can you prepare the shells ahead of time?

Yes, you can fill the shells the day before and keep them in the refrigerator. Just pop them in the oven the next day to finish the gratin.

Which white fish works best for this recipe?

Cod works great, but hake, pollock or whiting also work well. The key is choosing a fillet that flakes easily once cooked.

How do you keep the bechamel from going lumpy?

Add the milk gradually while whisking constantly over low heat. If lumps do form, a vigorous whisk usually smooths them out.

Do kids usually like this dish?

Yes, flaked fish under melted cheese tends to go over well since the flavor stays mild. The homemade mashed potatoes pair nicely with that soft texture kids tend to enjoy.

How long does it take to make gratinéed fish shell scallops with mashed potatoes?

Count 55 min in total, prep and cooking included. The recipe is rated “medium”.

How many calories are in gratinéed fish shell scallops with mashed potatoes?

About 750 kcal per serving, for a recipe meant for 4 people. Calories are calculated by Kiloach, your weight coach, the app that partners with Mon Chou.

How much does gratinéed fish shell scallops with mashed potatoes cost?

About €3.90 per serving, or €15.60 for 4 people, based on average supermarket prices.

What allergens does this recipe contain?

This recipe contains fish, lactose, gluten. Always check the labels of the products you buy.

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