1. Preheat oven to 350°F (175°C) and line two baking sheets with parchment paper.

2. In a medium bowl, whisk together flour, cocoa, milk powder, cornstarch, baking powder, baking soda, and salt.

3. In a large bowl, whisk butter, oil, brown sugar, and granulated sugar until smooth.

4. Add the egg and vanilla, mix well, then stir in vinegar and food coloring.

5. Add dry ingredients and fold gently until a thick, sticky dough forms.

6. Scoop large portions (3–4 tablespoons) of dough onto the sheets, leaving space between.

7. Bake for 12–15 minutes until puffed and lightly golden at the bottoms.

8. Cool cookies on the sheet for 5 minutes, then move to a wire rack to cool fully.

9. For frosting, beat cream cheese and butter until smooth.

10. Add vanilla and powdered sugar, mixing until creamy.

11. Spread or pipe frosting onto cooled cookies and garnish with cookie crumbs if desired.