In the bowl of your stand mixer, with the paddle attachment, beat butter 2 minutes, until light and fluffy. Add in light brown sugar, granulated sugar and vanilla bean paste. Beat 3 minutes until light and fluffy. Scrape down sides as necessary. Add in eggs and mix until combined.
In a medium bowl, whisk together flour, cornstarch, baking soda, and salt. While mixer is on low, add flour mixture to butter and mix until combined. Add in sprinkles and mix until just combined. Cover tightly with plastic wrap and chill for 2 hours.
Heat oven to 350F. Line 2 baking sheets with parchment baking paper and set aside.
Using a 2 tablespoon cookie scoop, roll cookies into balls, and place on prepared cookie sheets. Place additional sprinkles on the tops of each cookie. Bake for 11-12 minutes, or until golden on the edges. Cookie will look slightly under-baked.
Let the cookies rest on the baking sheet for 5 minutes, then transfer to wire rack to cool completely. Store in an airtight container.