1cup [226 grams]unsalted butter, at room temperature
1cup [200 grams]granulated sugar, plus more for rolling
¼cup [50 grams]light brown sugar, packed
1large egg plus 1 egg yolk
1teaspoonvanilla extract or vanilla paste
⅓heaping cuprainbow jimmies sprinkles
½ cup [85 grams]white chocolate chips or chunks
Instructions
In a small bowl, combine the flour, baking powder, baking soda, kosher salt, and cream of tartar and set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and both sugars on medium speed for 5 minutes until light and fluffy and pale in color. Add the egg and egg yolk one at a time until each is incorporated. Add the vanilla and beat on medium-low speed for another minute until fully combined. Scrape down the paddle and the bottom and sides of the bowl.
Add the flour mixture and beat on low speed until just combined, about 30 seconds. Scrape down the sides of the bowl. Add in the jimmies sprinkles and white chocolate chips and mix on low to incorporate, about 5-10 seconds.
Place plastic wrap over the top of the cookie dough and refrigerate for 1 hour to let all the ingredients get to know each other.
Adjust the oven rack to the middle position and preheat the oven to 350°F. Scoop the cookies using a 1-ounce cookie scoop to portion the dough and roll the cookies into a ball and roll into granulated sugar. Place onto a parchment-paper lined baking sheet.
Bake for 10-12 minutes. Transfer the baking sheet to a wire rack and let cool completely on the pan. Note: For perfectly round cookies, use a large cookie cutter or biscuit cutter (must be wider than the cookie) and swirl in a circular motion to shape the edges immediately after removing from the oven while the cookies are still hot.
Notes
To freeze the cookie dough, place the parchment paper-lined sheet pan with the scooped cookies in the freezer for about 20 minutes until the cookie balls are set. Then transfer the cookie dough to a freezer-safe plastic bag or container.