Boil rice in salted water. Froth the butter, sweat the flour and mustard in it, deglaze with the broth, add the cream and lemon juice and season with salt, pepper and sugar. Let the sauce cool a little and add the whisked egg yolks with the chopped dill. Butter the baking dish and fill in the well-drained rice. Salt and pepper the cleaned fish fillets, place on the rice and pour the sauce over them.
Bake in a preheated oven at 250 ° (gas mark 5, convection 225 °) for about 12 minutes until golden brown.