MIX butter, brown sugar and vanilla using a mixer. Gradually blend in flour and corn starch. Add chocolate chips.
FORM into 1-inch balls; place on ungreased baking sheets. Pour sugar on a small plate; dip bottom of drinking glass in sugar and gently press down on each cookie to flatten.
BAKE in a preheated 300°F oven for 25 to 30 minutes, or until bottoms begin to brown.
COOL for 5 minutes; remove to a wire rack to cool completely. Lightly sprinkle additional sugar on top of warm cookies, if desired.