Cream butter, oil, and sugar together until smooth and light. Stir in eggs and vanilla and whip until light and fluffy. Stir in dry ingredients slowly until all incorporated.
3/4 cup butter, 1/4 cup canola oil, 2 cups granulated sugar, 2 large eggs, 1 tablespoon vanilla extract, 3 cups all purpose flour, 1/4 cup cornstarch, 1 teaspoon baking soda, 3/4 teaspoon baking powder
Refrigerate dough for 2-3 hours.
Preheat oven to 350. Line baking sheet with parchment paper and set aside.
Remove cookie dough from the refrigerator and roll it out on a lightly floured surface. Cut into 2-inch circles and place 2 inches apart onto the prepared baking sheet.
Bake 7-9 minutes or until barely golden brown. Cool 5 minutes before removing to cooling rack.
For the frosting, stir butter, sugar, and vanilla together with the mixer on low. Slowly pour in milk until frosting starts to come together and becomes thick, light, and fluffy. {Go slow to make sure it stays on the thicker side!} Whip 1 minute.
1/2 cup butter, 1 lb powdered sugar, 2 teaspoons vanilla extract, 1-2 tablespoons cold milk
Spread each cookie with a generous amount of frosting and top with a variety of sprinkles. Serve.