Beat butter until light and fluffy, then beat in 2 tablespoons of the sugar, egg yolk, vanilla and almonds. Gradually add flour, beating to blend thoroughly. Pinch off pieces of dough the size of large walnuts and rolls between your palms into round balls. Place 4 cm apart on ungreased baking sheets; flatten each ball slightly. Bake in a 140ºC oven until very lightly browned (about 45 minutes). Let cool on baking sheets until lukewarm. Sift half the remaining powdered sugar onto a large sheet of wax paper. Roll each cookie gently in sugar. Wtih your fingers, pack more sugar all over cookies to a depth of about 0 cm. Place cookies on wire racks and dust generaouly with more powdered sugar; let cool completely. Store in airtight containers, layter between sheets of wax paper. Makes 3 dozen.