In a large mixing bowl, cream together the butter, oil, granulated sugar, and powdered sugar until light and fluffy. Add sour cream, eggs, and vanilla, and mix until combined.

In a separate bowl, whisk together the flour, baking soda, cream of tartar, and salt. Gradually add to the wet ingredients, mixing until a soft dough forms. It should be thick but not dry.

Cover the dough and chill for at least 1 hour. This helps the cookies hold their shape and get that classic soft-but-set texture.

When you’re ready to bake, preheat your oven to 350°F and line two baking sheets with parchment paper.

Scoop out about 2 tablespoons of dough and roll into a ball. Place on the baking sheet and flatten slightly with the bottom of a glass (you can lightly grease or sugar the glass to prevent sticking). Bake for 10–12 minutes—edges should be just set, but the centers will still look soft. Don’t overbake.

Let cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack. Once cooled, chill the cookies in the fridge before frosting for a true Swig-style finish.

Beat together the butter and sour cream until smooth. Add powdered sugar, vanilla, salt, and a splash of milk. Beat until creamy, adding more milk as needed to reach your preferred consistency. Add a few drops of pink gel food coloring until you achieve the perfect pink.

Spread a generous dollop of frosting on each cooled (and preferably chilled) cookie. Serve cold for the most authentic copycat experience.