In your cupcake or muffin tin, spray nonstick cooking spray. In one cup at a time, pour a teaspoon of cocoa powder in. Tap the powder until it covers the entire cup. Repeat to the rest of the cups.
In a microwave safe bowl, add the chocolate chips, butter, and heavy cream. I used regular milk since I didn't have heavy cream and it worked fine.
Microwave in 30 second intervals and stir the chocolate each time afterwards. Repeat until the chocolate is melted and smooth.
In a separate bowl, add the sugar and flour. Whisk until combined.
Add the eggs to the dry mixture and whisk until incorporated.
Slowly poor into the chocolate mixture and whisk constantly. Continue to whisk until everything is combined.
Pour into the cupcake/muffin tin. Let it sit in the fridge for at least an hour. It can sit in the fridge for an entire day.
Preheat the oven to 450 degrees.
Place pan in the oven for 10 minutes for a cupcake tin and 17 minutes for a large muffin tin or until the top centers are barely cooked. They won't still be a batter. This will help keep the gooey chocolate inside until the cake is cut into.
Take the lava cakes out of the oven and let them sit in the pan for 10 minutes.
Place a plate on top of the tin to flip the cakes out. Flip the tin over with the plate still on top. The cakes should come out perfectly.
Serve with ice cream or fresh fruit. Whatever your heart desires, actually.