Add the room-temperature vegan butter, cane sugar, and brown sugar to a large mixing bowl. Cream together until light and fluffy using a hand mixer or stand mixer.
Add the vanilla extract and applesauce. Beat together on high for one minute.
Sift together the flour, cornstarch, baking powder, and baking soda.
Slowly add the flour to the butter mixture until the flour is completely incorporated.
Cover and chill the cookie dough for 30 minutes.
Preheat the oven to 350°F. Line a baking sheet with parchment paper.
Add one tablespoon scoops of the chilled dough to the prepared baking sheet 2 inches apart to leave room for spreading.
Bake for 10-12 minutes on the center rack or until lightly golden brown on the bottom.
Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a cooling rack to cool completly.
Once cooled, spread the vegan buttercream on top of each cookie ad top with holiday sprinkles.