1/4 cup dry red wine
1/4 cup dry sherry
3 tablespoons balsamic vinegar
1 shallot, chopped
2 garlic cloves, chopped
2 egg yolks
1/3 cup unsalted butter, melted
Bring first 5 ingredients to a boil in a small saucepan; cook 2 minutes. Cool mixture.
Whisk egg yolks into wine mixture, and cook over low heat, whisking constantly, until thickened. Slowly whisk in butter until blended. Serve immediately.