Soft Sugar Cookies with Buttercream Frosting

Soft Sugar Cookies:
2 Line 2 cookie sheets with parchment paper and set aside. Pre-heat your oven to 350 Fahrenheit
10 In a separate bowl, mix the dry ingredients (flour, baking soda, and cornstarch). 
3 In a bowl of a stand mixer with the paddle attachment on medium-high speed or with an electric hand mixer, mix sugar, room temperature butter, oil, and salt, until no lumps are visible and the butter is creamed. Add in egg and yolk, vanilla extract and mix
4 Mix in the flour mixture and mix until just combined. Do not over-mix! These cookies will need 30 minutes of chill time, so cover the mixing bowl and pop them in the fridge before continuing to the next step.
5 Remove the chilled cookie dough from the fridge. Using a 3 Tablespoon cookie scoop, scoop the batter and place it on the prepared cookie sheets leaving space between them -no more than 6 cookies per sheet. Bake for 11 minutes, until edges are golden brown but the center is still gooey. Cookies may seem a bit underbaked, but they will finish baking on the cookie sheet.
6 Using the bottom of a flat glass, press cookies flat while still hot, to around 3/4" thick. Transfer them to a cooling rack and let them cool completely before frosting.
Buttercream Frosting:
9 Cream butter on medium speed with an electric mixer, until light and fluffy. With the mixer running at low speed, add the sifted powdered sugar, vanilla extract, and salt. Turn speed up to medium-high and beat until light and fluffy. Add pink gel food coloring, drop by drop, until reaching the desired shade of pink. Using a butter knife, swirl the top of the cookie with frosting and decorate with sprinkles.