• Preheat the oven to 350°F. Line baking sheets with silicone baking mats or parchment paper and set aside.

Make the cookie dough.

• In a small bowl, whisk together flour, cornstarch, baking powder, baking soda, and salt. Set aside.
  1 ⅔ cups all-purpose flour, 2 teaspoons cornstarch, 1 ¾ teaspoons baking powder, ¼ teaspoon baking soda, ¼ teaspoon salt
• In the bowl of a stand mixer using a paddle attachment (or in a large bowl using an electric hand mixer), cream butter and sugar by first beating butter on high speed until smooth and creamy (about 30 to 60 seconds) and then adding sugar and beating on medium-high speed until light and fluffy (about 2 minutes).
  5 Tablespoons unsalted butter, ⅔ cup granulated sugar
• Add egg to the creamed butter and sugar and beat on medium-high speed until well blended.
  1 large egg
• Add cream and vanilla and beat on medium-high speed until combined.
  ⅓ cup heavy whipping cream, ¼ teaspoon vanilla extract
• With the mixer running on low speed, slowly add the flour mixture to the butter mixture and stir just until blended. 
• Use a cookie scoop or large spoon to scoop 1 ½ Tablespoons of cookie dough into balls. Place cookie dough balls at least 2 inches apart on the prepared baking sheets.

Bake the cookies.

• Bake the cookies, one tray at a time on the oven's middle rack, for 10-12 minutes or until the cookies are just golden at the edges. Let cookies cool for 5 minutes on baking sheets before transferring to a wire rack to cool completely.

Make the buttercream frosting.

• When cookies have cooled, make the buttercream frosting. In the bowl of a stand mixer using the paddle attachment (or in a large bowl using an electric hand mixer), beat butter on medium-high speed until smooth. Add vanilla and salt and beat on medium-high speed until blended.
  ½ cup unsalted butter, ½ teaspoon vanilla extract, 1 pinch fine sea salt
• Slowly add sugar, beating well on medium speed and scraping the bowl often. When all sugar is added the frosting will be slightly dry.
  1 ⅔ cups confectioners' sugar
• Add cream and beat on high speed until the frosting is light and fluffy. If using food coloring, add one to two drops and blend thoroughly into the frosting. Add more food coloring, a tiny bit at a time, until the desired color is reached.
  2 Tablespoons heavy whipping cream

Decorate the cookies.

• Decorate the cookies by spreading the frosting onto the cookie and immediately topping them with sprinkles. Or get creative any decorate them any way you like!