1/2 cup butter
1/2 cup brown sugar
1/3 cup granulated sugar
1 large egg
2 teaspoons vanilla extract
1 1/2 cup all-purpose flour
2 teaspoons cornstarch
1 teaspoon baking soda
1/4 teaspoon salt
1 cup milk chocolate chips
Preheat oven to 350°F. With a stand or hand mixer cream together the butter and both sugars on medium-high speed until light and fluffy, about 4 minutes. Add egg and vanilla, and mix until combined, about 1 minute.
Add in the flour, cornstarch, baking soda and salt, and beat on medium speed until combined.
Gently fold in the chocolate chips by hand until just combined. Chill overnight ( if you can wait!) If not chill the dough at least 20 minutes.
Scoop dough into 1 inch balls that are about 1-inch in diameter, and place them on a greased baking sheet.
Bake for 10-12 minutes until the edges are just set.