1 oz. semisweet chocolate, chopped
1 tablespoon unsalted butter
1/2 teaspoon vanilla extract
Microwave 1 oz. chocolate and 1 tablespoon butter in small microwave-safe bowl on medium 1 minute or until melted; whisk until smooth.
Whisk in 1/2 teaspoon vanilla; cool until slightly thickened.
With small fork or whisk, drizzle glaze over cake. Cover and store in refrigerator.