1. Choose the thickest center section of the fish. Using a flexible boning knife, cut apart the two fillets, and carefully remove skin.

2. With pliers, pull out the tiny bones hiding in the center of the flesh. They can be found by running fingers against the grain of the fish. Divide the fillets in half horizontally to make four pieces weighing about 6 ounces each.

3. Lightly oil two pieces of parchment paper with peanut oil. Lay one piece of parchment on a flat surface. Place fish on parchment. Top with second piece of parchment. With a wooden mallet or the side of a cleaver, gently flatten so each fillet is of equal thickness.

4. In a medium saucepan, combine fish stock and shallots. Bring to a boil, and cook until reduced to a glaze, 10 to 15 minutes. Add wine and vermouth, and continue to cook until bright and syrupy, about 3 minutes. Add creme fraiche, and boil until slightly thickened, about 2 minutes. Pass through a fine mesh sieve into a clean pan.

5. Add sorrel, and cook for 25 seconds. Remove from heat. Add butter a little at a time, swirling or stirring with a wooden spoon until completely incorporated (be sure not to break up sorrel leaves). Season with lemon juice, salt, and pepper.

6. Heat a large nonstick skillet over medium-high heat. Season salmon on one side (the less presentable side) with salt and pepper. Place in pan, seasoned side up. Cook 25 seconds, turn, and cook 15 seconds more. The salmon must be undercooked to preserve its tenderness (it will continue to cook in the finished sauce).

7. Distribute sauce among four large plates. Place salmon, seasoned side down, on plates. Season with salt. Serve immediately.