Georges's Butter Sauce

In a small nonreactive saucepan, combine wine and shallots. Bring to a boil, and cook until 1 tablespoon of liquid remains, about 5 minutes. Add cream, and reduce slightly. Add butter, a few pieces at a time, whisking constantly until fully incorporated. Work on and off heat as necessary to prevent sauce from breaking (separating). Pass through a fine-mesh sieve. Add curry, lemon juice, salt, and pepper. Add truffle juice, if desired. Set aside and keep warm.