Preheat oven to 350°F. Line baking sheets with parchment.

Mix cake mix, oil, and eggs until dough forms.

Scoop into 1-tbsp balls, flatten slightly, and bake for 8–10 minutes.

Cool on pan for 5 minutes, then transfer to rack.

Beat butter and cream cheese until smooth. Add powdered sugar, then milk for desired consistency.

Spread frosting on one cookie and top with another.

Serve immediately or store airtight.