01 -
Beat softened butter and granulated sugar together in a mixing bowl until light and fluffy.
02 -
Mix in the egg, egg yolk, and vanilla extract until smooth.
03 -
Blend in baking soda, cream of tartar, salt, and flour until dough forms.
04 -
Scoop 2-tablespoon portions of dough onto a baking sheet and bake at 350°F (175°C) for 11–15 minutes, until lightly golden at the bottom.
05 -
Let cookies cool on the baking sheet for 10 minutes before transferring to a wire rack. Cool completely before frosting.
06 -
Mix softened butter, powdered sugar, vanilla extract, salt, and milk until smooth. Add food coloring if desired.
07 -
Frost cooled cookies and decorate with sprinkles as desired.