For the cookies… 1 stick unsalted butter, soft 3/4 cup white granulated sugar 1 large egg 1 teaspoon pure vanilla extract 1 1/2 cups white all-purpose flour 1 teaspoon baking powder 1 teaspoon cream of tartar 1/2 teaspoon baking soda 1/2 teaspoon salt For the frosting… 1 stick unsalted butter, soft 3 cups powdered sugar 2 teaspoons pure vanilla extract 1/2 teaspoon salt Splash of whole milk Food coloring, if desired Start first by making the cookies, by combining the soft unsalted butter with the white granulated sugar in a large bowl until light and fluffy. Beat in the large egg and pure vanilla extract. Beat in the white all-purpose flour, baking powder, cream of tartar, baking soda and salt until just combined. Roll this dough into balls the size of two tablespoons and place on a greased plate. Once the balls have all been rolled, cover with plastic wrap and refrigerate them overnight. When ready to bake, preheat oven to 350 degrees F. Line two large baking pans with parchment paper. Place the balls evenly between the two pans, allowing some space between for the cookies to spread. Place, one sheet at a time, in preheated oven for 8 minutes. After 8 minutes, remove and flatten each ball slightly with the bottom of a drinking glass. Return the cookies to the preheated oven for 4 more minutes to continue baking through. Once baked, remove and allow to cool before frosting. To make the frosting combine the soft unsalted butter with the powdered sugar using a whisk. Add in the pure vanilla extract and salt. Gently whisk in the whole milk until you get your desired frosting consistency. The frosting should be thick but spreadable. Add in food coloring if desired. Frost cookies and serve.