Preheat the oven to 325 degrees. Cream the butter, sugar and vanilla in a small bowl at medium speed until light and fluffy. Gradually add the flour, mixing at low speed until blended. Press onto the bottom of a 9-inch springform pan; prick with a fork.
Bake 25 minutes or until the edges are light golden brown.
Filling:
4-8 ounce packages cream cheese, at room temperature
½ cup sugar
1 teaspoon vanilla
4 large eggs
12 ounces white chocolate, melted, slightly cooled
Beat the cream cheese, sugar and vanilla at medium speed until well blended. Add the eggs, one at a time, mixing at low speed after each addition, just until blended.
Blend in the melted chocolate; pour over the crust.
Bake 55 to 60 minutes or until the center is almost set. Run a knife around the rim of the pan to loosen the cake; cool before removing the rim of the pan. Refrigerate overnight. Garnish with chocolate curls and powdered sugar.
Source: Best Loved Chocolate Recipes, Publications International, Ltd., 1997