Preheat the oven to 300° F.
Using a stand mixer fitted with a paddle attachment, beat the room temperature butter and powdered sugar on medium-high speed for about 5 minutes, until it's light and fluffy. Scape down the sides of the bowl. You can use an electric hand mixer and a large bowl if you don’t have a stand mixer.
Add in the flour, ¼ cup cornstarch, vanilla extract and almond extract on low speed. Scrape the bottom of the bowl to make sure all ingredients are incorporated.
Dust your hands lightly with some cornstarch to keep the dough from sticking to your hands.
Using a cookie scoop, scoop about one tablespoon of the shortbread dough into your hands and roll into a ball.
Place the cookie dough ball onto a parchment paper lined cookie sheet and repeat with the remaining dough.
Dip a fork into extra cornstarch and lightly press the tines of a fork on top of the cookie ball. Top with sprinkles of your choice.
Bake cookies for about 15 minutes in the middle of the oven, removing before they begin to brown.
Transfer to a cooling rack after about 5 minutes to cool completely.