Chocolate Cheesecake Squares

1 c all-purpose flour, unsifted
1/2 c sugar
3 T cocoa
1 t baking powder
1/4 t salt
1/2 c butter
1 egg, separated
1 t vanilla
1/2 c walnuts
Cheesecake filling (recipe follows)
1 square (1 oz) semisweet chocolate

Line the bottom and two opposite sides of a 9-inch square pan with a strip of foil that overlaps the sided of the pan, grease foil and all pan sides. Using metal blade process flour, sugar, cocoa, baking powder and salt for 2 seconds. Cut butter into chunks. While processor is running drop chunks down feed tube, one at a time, and process until mixture looks like cornmeal. Add egg yolk (save white for filling), vanilla and nuts, process until mixture forms a ball and nuts are coarsely chopped. Press mixture into prepared pan. Bake in 325 oven for 15 minutes. Remove crust from oven, let cool 5 minutes, then slowly pour cheesecake filling over crust. Return to oven and continue baking for 20 minutes or until filling is set. Cool in pan for 1 hour, then garnish top with chocolate curls made by scraping the square of chocolate (at room temperature) with a vegetable peeler. Cover and chill well. To serve, lift cheesecake from pan with foil sling, then cut into small squares. Makes 25 pieces.

Cheesecake filling
Orange zest
1/3 c sugar
1 package (8 oz) cream cheese
1/2 c sour cream
1 T flour
1/4 t salt
1/2 t vanilla
1 egg + reserved egg white

Cut a 1/2 by 3 inch strip of zest (colored part of peel) from and orange, cut zest into quarters, Using metal blade process zest and sugar until zest is finely chopped. Cut cream cheese in chunks, add to sugar and process until creamy. Add sour cream, flour, salt, vanilla, egg and reserved egg white. Process until smooth.