Rinse plaice fillet cold and dab dry. Cut lengthwise in half. Cover one half of the fillet with a halved slice of salmon and roll up. Stick together with wooden skewers. Boil up plenty of water with salt and lemon juice (keep 2 tablespoons).
Add the fish rolls and let them simmer at low heat for about 10 minutes. Finely dice the shallots and fry them in hot oil. Pour on white wine and let it boil down a little. Wash the dill, dab dry and chop. Remove wine stock from the stove and stir in sour cream. Do not let it boil up any more. Add dill. Season sauce with remaining lemon juice, salt and pepper. Cut fish rolls into slices and arrange on four plates with the sauce.
Remove wine stock from the stove and stir in sour cream. Do not let it boil up any more. Add dill. Season sauce with remaining lemon juice, salt and pepper. Cut fish rolls into slices and arrange on four plates with the sauce. Garnish with dill and dill flowers as desired