Preheat the oven to 425°F.

Spray the cups of a 12-cavity muffin pan thoroughly with nonstick cooking spray.

Microwave the chocolate chips and butter together in 30-second increments until fully melted. Stir to combine.

Mix together the eggs and egg yolks in a large mixing bowl. Stir in the powdered sugar, flour, and salt. Whisk the mixture until only a few small lumps remain. Fold in the melted chocolate until thoroughly combined.

Scoop the batter into the prepared muffin pan cups, filling each about 3/4 full.

Bake the cakes on middle rack of oven until they have formed a crust on top, about 9 minutes.

Check to see that cakes are done. Remove from oven or add time as needed.

Cool the cakes in the pan for 3 minutes. Invert the muffin pan onto a large cutting board to release the cakes. Serve immediately.