These are so easy! For the cookies you'll need butter, confectioners' sugar, sugar, an egg, vanilla extract, flour, salt, and baking powder.
For the frosting you'll need more unsalted butter, confectioners’ sugar, heavy cream or whole milk, vanilla extract, and a pinch of salt.
Cream together the butter and sugars until light and fluffy. Beat in egg and vanilla extract. Beat in dry ingredients. Chill dough briefly before scooping.
Scoop large cookies (I use a 1/3 cup scoop) and bake. Frost when cool.
Frosting: Whip the softened butter and confectioners' sugar until incorporated. Add in the heavy cream, vanilla extract and a tiny pinch of salt. Beat until light and fluffy.
Store frosted cookies in the fridge for up to 5 days. Use an air-tight container. Cookies can be gently layered (I suggest two layers max) between wax paper.