For the savoy cabbage roulades:
Blanch the savoy cabbage leaves in salted boiling water for 2 min. Immediately rinse in ice-cold water and pat dry with kitchen paper.
Remove the skin and bones from the brook trout fillets and cut out 8 pieces from the middle to fill the roulades with later. Cut the rest of the fish into small cubes and chill well. Place the well chilled fish cubes with salt, pepper and lemon juice in a blender and make a fish sauce with the cream. Refine the sauce with chopped dill and refrigerate. Next, remove the stalk from the savoy cabbage leaves and brush with the fish sauce. Place the fillet pieces in the middle of the roulade and roll up.
Place the savoy cabbage roulades in an oven dish and brush with melted butter. Season with salt and pepper and bake in the oven at 160 °C for approx. 25 min.
For the asparagus ragout:
In the meantime, peel the asparagus and cut into 2 cm pieces. Peel the carrots, halve them and cut them into thin strips. Clean the mangetout and cut them in half diagonally. Blanch the vegetables in boiling salted water for approx. 3 min. then rinse in ice-cold water.
For the sauce, finely dice the shallot and sauté briefly in the butter. Add the flour and stir. Add the stock and cream and boil the sauce well for 2 minutes.
Season to taste with salt, pepper and nutmeg. Add the vegetables just before serving and heat through.