1. Beat 1/2 cup softened butter and sugar in large bowl until creamy. Add egg and vanilla; beat until light and fluffy. Stir together flour, baking powder and salt; add to butter mixture, beating until soft dough forms.
2. Remove half the dough to medium bowl; blend in ground almonds and almond extract, if desired. Add cocoa and melted butter to remaining dough; blend well. Divide each dough in half. Refrigerate doughs, if necessary, until firm enough to handle.
3. Between 2 pieces of wax paper, roll one portion almond dough into 8-inch square; repeat procedure with one portion chocolate dough. Remove top sheets of wax paper; invert almond dough onto chocolate dough. Peel off top sheet of wax paper; roll up lightly. Repeat procedure with remaining doughs. Wrap both rolls in wax paper or plastic wrap; refrigerate 4 to 5 hours or until firm.
4. Heat oven to 350°F. Cut rolls into 1/4-inch slices; place 2 inches apart on ungreased cookie sheet.
5. Bake 9 to 12 minutes or just until set. Remove from cookie sheet to wire rack. Cool completely. Makes about 5 dozen cookies.
VARIATION: HOLIDAY CHOCOLATE-NUT PINWHEEL COOKIES: Stir 1 tablespoon finely chopped, well drained maraschino cherries into dough with ground almonds.