Source: Gourmet - December 1996

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

Chocolate Batter
3/4 stick (6 tablespoons) unsalted butter, cut into pieces
2 ounces unsweetened chocolate, chopped
2 ounces fine-quality bittersweet chocolate (not
    unsweetened), chopped
1 cup granulated sugar
1 teaspoon vanilla extract
2 large eggs
2/3 cup all-purpose flour
1/2 teaspoon salt

Preheat oven to 350 degrees F. Butter and flour a 9-inch square baking pan, knocking out excess flour.

Make cheesecake batter: In a bowl stir together cream cheese, sugar, and zest with a wooden spoon until smooth. Beat in egg with a fork until blended and stir in flour.

Make chocolate batter: In a heavy 1 1/2-quart saucepan melt butter and chocolate over low heat, stirring, until smooth and remove pan from heat. Cool mixture 10 minutes and stir in sugar and vanilla. Add eggs, 1 at a time, beating well with a wooden spoon until mixture is glossy and smooth. Stir in flour and salt until just combined.

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 brownies in middle of oven for 50 minutes, or until cheesecake mixture is pale golden and a tester comes out clean.

Cool brownies completely in pan on a rack before cutting into 16 squares. Brownies keep, layered between sheets of wax paper in an airtight container and chilled, 5 days. Brownies may be eaten chilled or at room temperature.