Instructions: Preheat oven to 350 degrees. Grease and flour a 9- by 13-inch pan, then line with waxed paper.

Beat together butter and shortening, gradually adding sugar. Beat well at medium speed on an electric mixer. Add softened cream cheese, beating well, until light and fluffy. Alternately add flour and eggs, beginning and ending with flour. Stir in vanilla.

Pour batter into pan, spreading batter to edges.

Bake for 35 to 40 minutes or until a wooden pick inserted in center comes out clean. Let cool in pan 10 minutes. Turn cake upside down on cookie sheet that has been lined with parchment paper. Cover top loosely with foil; place in freezer for cake to get firm. (It is easier to cut into squares when frozen.)

Cut off all four brown edges of cake (eat these or toss them). Cut cake into 1-inch squares using a very sharp knife. Do not use a bread knife; it tears the cake. Brush off any crumbs.

Prepare frosting.

Yields about 80 petit fours.

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