In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium speed until smooth and creamy, about 30 seconds.
1 cup salted butter
Add the milk and vanilla and mix to combine.
3 tablespoons milk, 1 tablespoon pure vanilla extract
With the mixer on low, slowly add the flour and powdered sugar. Continue mixing just until a shaggy dough forms.
2 cups all-purpose flour, ½ cup powdered sugar
Gently fold the sprinkles into the cookie dough.
¼ cup rainbow sprinkles
Shape the dough into a disc and wrap it in plastic wrap.
Place the dough in the fridge to chill for 15 minutes.
While the dough chills, preheat your oven to 350°F. Line a baking sheet with parchment paper. Set aside.
Lightly flour your work surface and roll the cookie dough out to ¼-inch thick. Cut the dough out using your choice of cutter (I used a 2-inch round cutter) and place the dough on the prepared baking sheet. These cookies don’t spread much so you only need to place them about 1 inch apart.
Bake for 14-16 minutes, or until the cookies are just starting to turn golden brown on the bottom.
Allow the cookies to cool completely.