2. In the bowl of a stand mixer fitted with a paddle attachment, cream together butter and sugars until fluffy and light in color. Add egg and vanilla and blend inches.
3. Mix in flour, cornstarch, baking soda and salt. Stir in chocolate chunks.
4. Using a standard-sized cookie scoop or tablespoon, drop dough onto a prepared baking sheet. Bake for 8-10 minutes, until barely golden brown around the edges. (The tops will not brown, but do NOT cook longer than ten minutes.).
5. Let cool, on the sheet, on a wire rack for five minutes. Remove from baking sheet and let cool completely. Makes approximately 3 dozen. Try not to eat them all.