Preheat oven to 350°F and line baking sheets.
Cream butter and powdered sugar until light and fluffy.
Mix in egg, vanilla, and almond extract.
Add flour, baking soda, and cream of tartar until combined.
Roll dough to about ¼-inch thick.
Cut into circles (I use a cup for easy, uniform cookies).
Place on baking sheets.
Bake 7–8 minutes—edges set, centers soft.
Cool completely (about 15 minutes).
Beat butter until smooth.
Add powdered sugar, vanilla, and salt.
Mix in heavy cream until fluffy.
Divide and color.
Use a 1 Tbsp scoop to add frosting to each cookie.
Spread it out and top with sprinkles.
