Mix butter, sugar, crushed candy and vanilla -- gradually blending in flour and corn starch. Form 1-inch balls and place on parchment paper-lined baking sheets.
Gently press down on each cookie to flatten. Bake in 300F degree oven for 25 to 30 minutes or until bottoms start to brown.
Cool and remove to a wire rack. Combine confectioners' sugar, milk and vanilla until frosting is smooth. Drizzle on cookies and sprinkle with crushed candy.