Cream together the butter, granulated sugar, and light brown sugar; mix in the egg until the wet batter is mixed together. Slowly mix in the flour ½ cup at a time; then fold in the salt, baking soda, cornstarch and whole pecans. Cover the cookie dough with plastic wrap and allow the dough to chill in the refrigerator for at least 30 minutes. 3 hours or overnight is best. Preheat oven to 350 degrees.