Step 2
Preheat oven to 350℉. Place a fine-mesh strainer over the mixing bowl and sift the flour, baking powder, baking soda, cornstarch, and salt into the wet ingredients. Stir batter with a wooden spoon until a soft ball of dough forms. Cover bowl with plastic wrap and freeze for 15 minutes. If the dough is too sticky to handle, put it back in the freezer for 5 minutes more.