Soft and chewy sugar cookies speckled with lots of colorful sprinkles!
Preheat oven to 350°F/180°C. Line 2 baking sheets with parchment paper. Set aside.
In a mixer bowl fitted with the paddle attachment, beat butter, granulated sugar, and powdered sugar on medium-low speed for 4 minutes. Beat in egg and vanilla extract just until combined. Add flour mixture and beat just until combined. Mix in sprinkles. Do not overmix.