• In a large bowl, cream 1 cup unsalted butter and 1 ¾ cup sugar until light and creamy. You can use a stand mixer fitted with a paddle attachment or a large bowl and electric hand mixer.
• Add 1 cup sour cream, 2 large eggs, and 1 teaspoon vanilla extract. Beat well, stopping to scrape the bottom and sides of your bowl, to incorporate ingredients until smooth.
• Add 3 ½ cups all purpose flour, 1 teaspoon baking soda, 1 teaspoon baking powder, and ½ teaspoon salt and beat on low until dry ingredients are combined.

  The dough will be very soft and this is what we’re looking for. Refrigerate overnight.
• Preheat oven to 350°F. Portion about 1 ounce of dough with a spoon, then roll into balls with lightly dampened hands.

  Add cookie balls to a parchment lined baking sheet.
• Bake 11 to 12 minutes, until the tops are set and the edges are lightly browned (the tops will still look a bit pale).
• Let sit on the baking sheet for 5 minutes, then transfer to a cooling rack.

  Allow cookies to cool completely before frosting.

To make buttercream frosting:

• Cream 1 cup unsalted butter at room temperature in a large bowl using a stand mixer with a paddle attachment or a hand mixer.
• Add 16 ounces powdered sugarr and mix on low-speed until all of the sugar is combined.

  Add in 1-2 Tablespoons whole milk as needed, 1 tablespoon at a time and 1 teaspoon vanilla extract to reach desired consistency.