Peel and wash the potatoes and cut them into large pieces. Cover and cook in boiling salted water for about 15 minutes
Mix vinegar, some sugar, salt and pepper. fold in the oil
Peel, wash and roughly grate the carrot. Clean, wash and drain the salad and pluck into pieces. Cut trout fillets diagonally into pieces. Arrange with salad on plates
Drain the potatoes, sprinkle with some marinade and press through a potato ricer. Add the potato mousse to the plates. Spread carrots over it, drizzle with the rest of the marinade. Add trout caviar and garnish with dill and coloured pepper if desired
Drink: cool white wine or dry sherry