Put 3 tablespoons of the butter in a 10- or 12-inch skillet over medium heat. When the butter melts, add the shallot and cook, stirring occasionally, until tender, 2 or 3 minutes. Add the wine and bay leaves, raise the heat to high, and cook until the mixture is reduced to about ½ cup, about 20 minutes.
Add the stock and reduce to about 1 cup, about 10 minutes.