Preheat the oven to 350 F. Line two greased cookie sheets with parchment paper.
In a bowl whisk together the olive oil, sugars and egg very well. Add the cornstarch, baking powder, soda, salt and flour and, using a rubber spatula, mix until well combined.
Use a cookie scoop to portion the dough, I use a 2 tablespoon scoop, leaving about two inches between each dough mound as these will spread.
Bake the cookies for about 10 minutes, at ten check on them - if they have the large crinkles they are done. If not or just beginning to, leave them in for another 2-4 minutes. Take them out when they are puffy, have wrinkles all over, and are dark on the edges. They will flatten as they cool.