Preheat oven to 350F. To make pastry, cream together butter and cream cheese. Add the white sugar, 2 cups flour and blend well. Shape into balls about 1-inch in diameter (flour palms of hands to facilitate rolling). Place ball in greased tartlet pan and flatten. Should fill pan by 3/4. To make filling: Mix together vanilla, egg, brown sugar, and chopped nuts. After flattening ball in tartlet tin, make a thumb print in center and fill with a full 1/2 tsp. of nut filling. Bake for 17-20 minutes. Cool completely before removing from pan.