Place shallot, bay leaf, peppercorns, vinegar, and wine in a saucepan. Bring to a boil, then reduce heat to medium and continue simmering until only 2 tablespoons of liquid remain.
Pour in heavy cream and bring to a simmer; simmer until the cream has reduced by half. Increase heat to medium-high, and rapidly whisk in the butter, piece, by piece until it has melted into the cream and thickened it. Strain the sauce through a mesh strainer to remove the spices. Serve immediately.
