1. Rinse salmon under running cold water and pat dry. Mix salt, sugar, pepper, and juniper berries in bowl; rub generously into skin of 1 piece salmon. Place skin side down in shallow dish. Sprinkle with some more salt mixture, top with dill and sprinkle with the 3 tablespoons gin. Top with second piece of salmon, skin side up. Rub skin with remaining salt mixture. Cover with plastic wrap. Weight down with cutting board, that fits just inside dish, topped with several heavy cans. Refrigerate 2 days or up to 1 week, turning every 12 hours and spooning juice over fish.Make Mustard Dill Sauce::
2. Dissolve dry mustard in gin in bowl. Let stand 30 minutes. Stir in remaining sauce ingredients.
3. To serve, remove salmon from marinade. Scrape away dill and spices; pat dry. Place skin side down on cutting board, cut diagonally into thin slices and remove from skin. Arrange slices on platter and garnish with dill. Serve with mustard sauce and toast triangles. Makes 12 servings.