Mix salt, sugar and white peppercorns. Take a handful and rub it on both sides of the salmon. Place the salmon in a dish and sprinkle the rest of the mix on top.
Cover the salmon with dill and let it stand for six hours at room temperature.
Put in the refrigerator for 24 to 30 hours, depending on how thick the salmon is.
Slice the salmon off the skin in thin slices, and place them on a platter. Cut the skin in pieces, approximately 1/2-inch wide, and blacken the skins in a very hot cast iron skillet.
Decorate the platter with lemon, dill and skin.
Mix the mustards, sugar and vinegar and season with pinches of salt and pepper. Mix in the oil while you pour it in a steady stream. When the sauce has a mayonnaise-like consistency, stir in the chopped dill.