This elegant dish is a simplified version of a traditional Scandinavian fish pie. Arrange it on a bed of fresh dill, garnish with lemon and orange slices, and slice diagonally. Serve with rye crisp, thinly sliced cucumbers, and grapefruit halves.
1. Thaw one sheet of puff pastry for about 20 minutes.
2. Trim and skin the salmon fillet. (Starting at the tail, work under the skin with a sharp knife until a small flap is completely loosened; hold the fillet down with one hand and pull the skin back, loosening with the knife as you go.) Trim off any fatty sections. Rinse under cold water to remove any scales, and pat dry.
3. Preheat oven to 400° F. Carefully unfold the pastry and roll out on a floured board until it is large enough to wrap around the fillet. Gently place the fish, skinned side down, on the pastry. Sprinkle with the dill, fennel seed, pepper, and shallots.
4. If the fillet is nearly rectangular, make a simple loaf shape by bringing the sides of the pastry up to the middle of the fish. Seal the fold with a small amount of lemon juice and water. Trim the excess pastry, seal the ends, and score the top layer diagonally.
5. If the fillet is triangular, have some fun and shape a head and tail with the pastry; shape excess into top and bottom fins, and snip out a mouth, gill slits, and scales — all above the fold — with kitchen scissors. Cut a small hole for an eye, and hold it open with a round ball of dough.
6. Bake for 25 minutes. Cool for 20 minutes and refrigerate overnight, wrapped in waxed paper and again in aluminum foil.To serve: Combine sauce ingredients in a small bowl. Remove the fish from the refrigerator and slice diagonally. Serve slightly chilled with the sauce, unwarmed, on the side.