Preheat oven to 350 degrees. Line cookie sheets with baking mat or parchment paper.
Whisk flour, baking soda, & baking powdered together, set aside.
Using a large mixing bowl add sugar, cream cheese & warm melted butter & whisk together. Whisk in oil. Add egg, milk, & vanilla. Whisk until smooth. Add flour mixture & mix with a spoon or rubber spatula until soft dough forms.
Take a large scoop of dough (about 2 Tablespoons worth) & roll into a ball. Place on prepared cookie sheets. Use the bottom of a drinking glass dipped in sugar to flatten dough balls slightly.
Bake at 350 degrees for 11-13 minutes or until edges are just starting to brown.
To make the frosting combine all 4 ingredients in a mixing bowl & use an electric mixer to mix ingredients until smooth. Once the cookies have cooled spread frosting over tops of cookies.
Recipe by THE SEMISWEET SISTERS at https://www.thesemisweetsisters.com/2015/05/15/the-best-chewy-frosted-sugar-cookies/