Adapted from the LA Times
5 ounces good quality white chocolate, finely chopped
1/3 cup heavy cream
2 teaspoons butter, at room temperature
Place the chocolate into a heat safe bowl. Bring cream to a boil (I microwaved in a Pyrex measuring cup till it started bubbling) and pour over chocolate. Stir till mixture is smooth, then add butter and stir till melted.
Cool till ganache is spreading consistency. Use to drizzle on or fill cookies.