Preheat oven to 350°F. Line 2 baking sheets with parchment paper. Set aside.
In a large bowl, whisk the flour, baking soda, cream of tartar, and salt together.
5½ cups all-purpose flour, ½ teaspoon baking soda, ½ teaspoon cream of tartar, 1 teaspoon kosher salt
In the bowl of a stand mixer fitted with the paddle attachment, cream the butter, oil, 1¼ cup granulated sugar, and powdered sugar until combined, scraping down the bowl as needed.
1 cup unsalted butter, ¾ cup vegetable oil, 1¾ cups granulated sugar, ¾ cup powdered sugar
Add in the milk and eggs. Mix until combined, again scraping down the bowl.
2 tablespoons milk, 2 large eggs
Add in the flour and mix on medium-low until just combined.
Add the remaining ½ cup sugar to a small bowl.
1¾ cups granulated sugar
Using a large cookie scoop, scoop and roll cookies that are about 3 tablespoons of dough. Roll the cookies in the sugar and line them up on the sheet pan about 3 inches apart.
Spray the bottom of a glass with nonstick spray. Press down on each cookie until they are about ½ inch thick. The edges will crack - that is what we are going for!
Bake for 8-10 minutes until the edges are set. The center of the cookie will not be fully baked - that is okay. Let the cookies cool on the cookie sheet for 5 minutes. Transfer them to a wire rack to cool completely.
While the cookies are cooling, make the frosting. In the bowl of a stand mixer fitted with the whisk attachment, beat the butter and sour cream until smooth and creamy, scraping the bowl as needed.
½ cup unsalted butter, 2 tablespoons sour cream
Add in the powdered sugar and salt, mixing until combined.
4 cups powdered sugar, 1 teaspoon kosher salt
Add in the milk and vanilla and mix again. Add pink or red food coloring until your desired color is achieved. These cookies are usually a pale pink.
1 teaspoon pure vanilla extract, 3-4 tablespoons milk, Pink food coloring
Frost cooled cookies with an offset spatula or butter knife. Serve and enjoy!