Preheat the oven to 425. Grease your jumbo muffin tin with either butter or non-stick cooking spray. Using a small sifter, generously dust cocoa on each of the tins. This will ensure the lava cakes won't stick.
Next, roughly chop your dark chocolate. Add it in to a microwave safe bowl with 1 stick of butter. Place in the microwave for 1 minute to 1 minute and 15 seconds. Take it out and then stir until the chocolate is beautiful, smooth and glossy with no lumps.
In a small bowl, mix the eggs and 3 egg yolks together. Add those to the bowl of chocolate as well as the vanilla extract. Next, add in the powdered sugar and flour. Mix gently until combined and no lumps are in the batter.
Add the batter into equal amounts into the muffin tin cups. Bake for 8-10 minutes until the outside ring of the cakes look done. The inside will still be gooey - which is what you want! Using a bread knife or your preferred tool, gently remove the lava cakes from the muffin pan. Enjoy warm with more powdered sugar sifted on top.
I used a jumbo 6 tin muffin pan. Feel free to use a 12 tin muffin pan - just make sure the batter gets evenly distributed between each tin :)