Cheesecake Batter
8 ounces cream cheese softened
1/3 cup granulated sugar
3/4 teaspoon finely grated orange zest
1 large egg 1 tablespoon all-purpose flour

Preheat oven to 350 degrees F. Butter and flour a 9-inch square pan. In a bowl stir together cream cheese, sugar and zest with a wooden spoon until smooth. Beat in egg with a fork until blended, stir in flour. Meanwhile, prepare Chocolate Batter.

Chocolate Batter
6 tablespoons butter, cut into pieces
2 ounces unsweetened chocolate, chopped
2 ounces semisweet chocolate, chopped
1 cup granulated sugar
1 teaspoon vanilla extract
2 large eggs
2/3 cup all-purpose flour
1/2 teaspoon salt

In heavy 1 1/2-quart saucepan, melt butter and chocolates over low heat until smooth. Cool mixture 10 minutes, then stir in sugar and vanilla extract. Add eggs one at a time beating well with a wooden spoon until smooth and shiny. Stir in flour and salt.

Spread Chocolate Batter evenly in pan. Drop Cheesecake Batter by large spoonsful onto Chocolate Batter and run a knife through batters to make decorative swirls. Bake in the middle of the oven for 50 minutes or until cheesecake mixture is pale golden and a tester comes out clean.

Cool completely in the pan on a rack.