Preheat the oven to 400 degrees F and line a 12-cup muffin pan with paper liners.
Add the cake mix to a large bowl and set aside.
Combine the yogurt, melted butter, eggs, and vanilla in a bowl or large measuring cup and whisk until smooth.
Pour the wet ingredients over the cake mix and stir until almost completely incorporated, but the dry mix is still streaking the batter.
Add the chocolate chips. Gently fold into the muffin batter until the chocolate chips are evenly distributed and no streaks of cake mix are showing. The batter will be very thick.
Divide the batter among the 12 muffin cups. It will look like too much batter but that’s ok, the batter will fill the cups and rise into big bakery-style muffins.
Bake the muffins at 400 degrees F for 15-18 minutes until lightly browned around the edges and a toothpick inserted comes out clean.