Knead flour, cold fat in pieces, salt and 4 tablespoons of cold water. Cover and chill for 1 hour. For the topping, clean and wash the onions and cut them into rings. Divide halibut into pieces. Whisk eggs, cream, thyme, salt and pepper. Roll out the dough slightly larger than the moulds (approx. 10 cm Ø).
Line greased ramekins with the dough. Spread onions and halibut on top. Pour egg-cream over it. You can use 1 large mould (approx. 28 cm Ø) instead of 6 moulds. Bake in the preheated oven (electric cooker: 200 ° C / gas: level 3) for 30-40 minutes