Cut the salmon in half lengthwise, and remove the backbone and small bones. Try to get your fishmonger to do this for you. Place half the fish, skin-side down, in a deep baking dish or casserole 4 to 6 inches (10 to 15 cm) high. Lay the bunch of dill evenly on the fish.
Combine the salt, sugar, and crushed peppercorns in a bowl. Sprinkle this mixture evenly over the dill. Drizzle the vodka over the salt and sugar mixture. Top with the other half of the fish, skin-side up.
Cover the top of the fish lightly with foil and place a dish or platter slightly larger than the salmon on top of it. Pile the dish or platter with weights to allow the marinade to permeate the fish. Cans of food work well. Refrigerate 48 to 72 hours.
Take the fish out of the dish every 8 to 12 hours, turn it over, and drizzle it with the liquid that accumulates around it. Make sure to separate the halves and baste the salmon inside. Replace the covering dish or platter and the weights each time.
You will notice that the fish becomes more compressed with each turning. Before serving, throw away the dill and seasoning, and pat the fish with paper towels to dry, making sure to remove all the peppercorns. Try one slice. If too salty, rinse the fish lightly under cool water and pat dry before slicing.
Place the separate halves skin-side down on a carving board and slice the salmon thinly (but slightly thicker than smoked salmon slices) on a diagonal, leaving the skin behind.
Arrange 2 to 3 pieces of the gravlax on a plate, spoon some Mustard-Dill sauce on the side and accompany with buttered rye bread. You could also make open-faced sandwiches or hors d'oeuvres. In that case, top the salmon with a dollop of sauce and a tiny dill sprig.
Mustard-Dill Sauce
Makes about 3/4 cup (180 mL)
1 Tbsp. (15 mL) grainy mustard
3 Tbsp. (45 mL) Dijon mustard
1 tsp. (5 mL) powdered mustard
2 Tbsp. (30 mL) sugar
2 Tbsp. (30 mL) white vinegar
1/3 cup (80 mL) canola or safflower oil
2 to 3 Tbsp. (30 to 45 mL) fresh chopped dill
Mix the three mustards, sugar, and vinegar in a small bowl. Slowly whisk in the oil. The sauce will thicken. Stir in the chopped dill.