Cream butter in a large mixing bowl; gradually add sugar, beating until light and fluffy.
Combine flour and baking powder in a medium mixing bowl; mix well. Add flour mixture and vanilla to creamed mixture, stirring well.
Divide dough in half; shape each half into a roll, 1 1/2 inches in diameter. Wrap each roll in waxed paper, and refrigerate 2 hours.
Cut rolls into 1/4-inch slices. Place on lightly greased cookie sheets. Brush lightly with egg white; sprinkle with almonds. Bake at 425° for 10 minutes or until lightly browned. Remove to wire racks to cool.