Heat oven to 350°F. Line two baking sheets with parchment.
Whisk eggs, oil, and vanilla in a large bowl until glossy.
Stir in cake mix, cocoa, baking powder, and salt until a soft dough forms.
Fold in mini chocolate chips.
Scoop 12 dough mounds, about 3 tbsp each, onto sheets. Gently flatten.
Bake 9–11 minutes until edges set and tops look matte. Cool 10 minutes, then move to a rack.
Warm cream in a small saucepan until steaming. Pour over ganache chips, butter, and a pinch of salt in a bowl.
Let stand 2 minutes, then stir until smooth. Cool 10–15 minutes until thick enough to spread.
Swirl ganache over fully cooled cookies. Let set before serving.