Beat 1/2 cup butter with flour, cornstarch, sugar, ground almonds, and vanilla. When dough begins to clump, take it up and shape into a cylinder. Divide dough into 4 equal portions. Pinch and press each portion into a 12- to 14-inch rope, about 1/2 to 3/4 inches in diameter. Gently roll on a smooth surface to smooth out wrinkles and cracks. Cut each rope into 2-inch lengths and place on ungreased baking sheets. Bake in a preheated 350° oven for 18 to 20 minutes, or until just golden on bottoms. Cool on wire racks.
In a double boiler over hot water, combine semisweet chocolate with 2 tablespoons butter. Heat over low heat, stirring occasionally, until chocolate is melted and well blended. Dip half of each cookie into the chocolate, then dip into chopped almonds. Place on wire rack over waxed paper for drips. Let cool until chocolate is set.