Preheat the oven to 450°F and coat four 6-oz ramekins with cooking spray. Set aside.
In a large glass measuring cup, melt chocolate chips and butter in 30-second increments until smooth.
Add vanilla, salt, and stir. Incorporate eggs, egg yolks, and flour. Pour batter into ramekins, filling about 2/3 full.
Place ramekins on a sheet tray and bake at 450°F for 8-10 minutes until edges set but the center is sunken.
Invert cakes onto plates immediately, dust with powdered sugar, and serve with raspberries or vanilla ice cream.
Notes
- To prep ahead, cover filled ramekins and refrigerate. Batter can be made a day ahead.
- No ramekins? Use a greased muffin pan for 6 slightly smaller cakes; start checking doneness at 6 minutes.
- Invert cakes by placing a heat-safe plate on top, flipping, and carefully lifting off the ramekin.
- Reheat in the microwave for 20-30 seconds, though the center won't be as gooey.