Preheat oven to 350°F (175°C) and line baking sheets with parchment paper.
In a large bowl, cream together butter, oil, granulated sugar, and brown sugar until smooth and fluffy, about 2 minutes.
Mix in egg, milk, vanilla, vinegar, and red food coloring until fully combined.
In a separate bowl, whisk together flour, cocoa powder, baking powder, baking soda, and salt.
Add dry ingredients to wet ingredients and mix just until combined. Do not overmix.
Scoop dough into large portions (about ¼ cup each). Roll into balls and gently flatten slightly.
Chill dough balls for 20–30 minutes (this helps keep them thick).
Bake for 10–12 minutes, until tops are just set and centers look soft.
Let cookies cool completely before frosting.