1 1/4 cups unsifted all-purpose flour
1 1/4 cups confectioners' sugar
3/4 cup unsweetened cocoa powder
1 cup cold unsalted butter
8 ounces cream cheese, softened
1 (14 ounce) can sweetened condensed milk
1 large egg
2 teaspoons vanilla extract
1/2 cup semisweet chocolate chips
1/2 cup chopped walnuts
Preheat oven to 350 degrees F.
In a bowl, mix flour, sugar and cocoa powder with a pastry blender. Cut in the butter until mixture resembles coarse crumbs. Press all but 2 cups of the mixture over the bottom of a 9 x 13-inch baking pan. Bake for 15 minutes.
Cut up the cream cheese and place in a large bowl. With mixer at high speed, beat until fluffy. Decrease to medium speed and gradually beat in sweetened condensed milk until blended. Beat in egg and vanilla extract. Pour over the baked crust.
Add chocolate chips and walnuts to the reserved crumb mixture. Mix well. Crumble this over the cream cheese mixture and bake for 25 minutes or until a wooden pick inserted in the center comes out clean. Cook on a wire rack, then refrigerate until firm.
Cut into squares. Store in the refrigerator.