Mix flour and baking powder. Beat butter and sugar in large bowl with mixer until light and fluffy. Blend in egg yolks and vanilla. Gradually beat in flour mixture until blended. Shape into 48 balls, using about 1 tablespoon for each.
Beat egg whites lightly. Dip dough balls, 1 at a time, in egg whites, then roll in nuts until evenly coated. Place 1 inch apart on parchment-covered baking sheets. Press your thumb into centres to indent.
Bake 12 to 14 minutes or until edges are golden brown. Cool on baking sheets 5 minutes. Remove to wire racks; cool completely.
Spoon cream cheese into pastry bag fitted with star tip. Use to pipe cream cheese onto cookies, adding about 1 teaspoon to each.