2 tablespoons extra-virgin olive oil
2 medium shallots— finely chopped, 1 halved
Freshly ground pepper
2 3/4 cups dry white wine
2 lemon thyme sprigs
1 bay leaf
4 6-ounces skinless salmon fillets
1 stick cold unsalted butter, cut into tablespoons
In a large skillet, heat the olive oil. Add the chopped shallots and season with salt and pepper. Cook over moderate heat until softened, about 3 minutes.
Add 1/4 cup of the wine and cook until evaporated, about 2 minutes.
In a large, nonreactive saucepan, combine 2 cups of the wine with the thyme, bay leaf, the halved shallot and 2 cups of water and bring to a simmer. Season the salmon with salt, add the fillets to the saucepan and cook at a bare simmer over low heat, turning once, about 6 minutes. Transfer the salmon to a plate and pat dry with paper towels. Discard the poaching liquid.
Add the remaining 1/2 cup of wine to the saucepan and bring to a simmer. Whisk in the butter, 1 tablespoon at a time, until thoroughly incorporated. Season with salt. Top salmon with the butter sauce and serve.