Preheat the oven to 375°.
In the bowl of a stand mixer, make the cookie dough by creaming together the butter and sugars.
Scrape the sides of the bowl and add in the eggs and vanilla. Mix until well combined.
Lastly, add the flour, yellow cake mix, corn starch, baking soda and salt to the bowl. Mix until thoroughly combined. The dough will be soft.
Portion the dough out into generous 1/3 of a cup portions. Roll into balls, flatten just slightly, and arrange on a baking sheet. Arrange 6 on each tray.
Bake at 375° for 9-11 minutes. Pull them out of the oven when the cookies have spread and the edges are turning golden brown.
Immediately after pulling the cookies out of the oven, make the buttery glaze.
In a small saucepan over medium heat, whisk together the butter and powdered sugar. Whisk until the powdered sugar combines with the melted butter in a creamy mixture.
Add in the butter vanilla emulsion. Stir to combine.
Use a pastry brush to brush the glaze on top of the hot cookies.
Allow the glaze topped cookies to cool for 10 minutes before dusting with powedered sugar.