Cream earth balance spread, brown sugar, vanilla, and egg together for a minute on medium speed.
Mix dry ingredients, flour, cornstarch, and baking powder in a separate bowl. I use a whisk to blend the dry ingredients or sift the dry ingredients.
Add dry ingredients to your wet ingredients. Mix until the cookie mix becomes like dough.
The dough will be sticky, so put the bowl in the refrigerator for 20 to 30 minutes. This will allow your dough to firm up a bit for rolling. The soy-free spread will make the dough soft, so more chill time is necessary.
Preheat oven to 375 degrees F. Flour the surface and very gently roll the dough out to ¼ inch thick. Cut your cookies out into desired shapes.
Place cookies on a baking sheet and bake for 6-7 minutes or when the cookie puffs up. Once baked, let sit for 5 minutes on the cookie sheet to firm up. Transfer to a cooling rack.