Melt the fat in a larger pot, dust with flour and sauté. Add cream and milk while stirring and simmer for about 2 minutes. Season to taste with salt, pepper and lemon juice.
Cook the pasta in boiling salted water according to the instructions on the packet. Wash the fish, dab dry and add to the sauce, cover and cook over a low heat for 8-10 minutes. Wash chervil, dab dry and put 4 stems aside for garnishing.
Finely chop the rest. Carefully crush the salmon into individual slices with a pallet or skimmer. Fold chervil into the sauce. Drain the pasta thoroughly, put it back into the pot and mix carefully with the sauce.
Arrange the pasta on preheated plates. Spread about 1 teaspoon of trout caviar over each noodle and garnish with lemon and chervil.