Cod fillet on potato gratin with mustard and saffron butter

Ingredients for 4 servings:

• 1 kg potatoes
• 80 g butter
• ¼ liter whipped cream
• 4 cod fillets (200g)
• 3 tbsp lemon juice
• 20 g flour
• ⅛ liter fish stock
• 1 pinch of saffron powder
• 2 tbsp sour cream
• 2 egg yolks
• 2 tbsp mustard (Dijon mustard)
• salt and pepper

Instructions

Working time approx. 55 minutes; Total time approx. 55 minutes

Peel the potatoes, cut into thin slices and cook in boiling salted water for 5 minutes, then drain and let cool slightly. Lightly grease 4 ovenproof dishes with butter and layer the potato slices in a layered manner. Spread 1/8 l of the cream on top and season lightly with salt. Cook the gratins in a preheated oven at 175°C for 30 minutes. In the meantime, drizzle the fish fillets with lemon juice, season with salt and a little pepper and chill. Foam 30 g of butter in a saucepan (refrigerate the remaining butter again). Sauté the flour in the butter, add the fish stock and remaining cream and bring to a boil. Dissolve the saffron in the sauce and simmer gently for 10 minutes, stirring occasionally. Add the cold butter in flakes to the sauce and mix with the two egg yolks (the sauce must no longer be boiling). Finally, stir in the mustard and season with lemon juice. Pour the sauce over the fish fillets and bake in the oven for another 12 minutes at 200°.