Buttery Shortbread Cookies

1. In a stand mixer, add cold butter slices and brown sugar. Use the paddle attachment on medium-high until combined and pasty. Scrape down sides as needed.
2. Add flour. Mix on medium-low until just combined.
3. On a floured counter or board, transfer dough and knead by hand, adding remaining flour only as needed until dough is soft, like playdough. Mix in sprinkles, if desired.
4. Divide into 3 discs, wrap, and chill for 30 minutes.
5. Heat oven to 325°F. Line baking sheets with parchment.
6. Roll dough to 1/2 inch thick. Cut into shapes and place on baking sheet. Chill for 15 minutes.
7. Bake for 15-20 minutes, until edges are golden. Cool completely on a rack. Enjoy!