Melt the butter and chocolate together over a double-boiler, or microwave for a short time.

Stir to combine.

Whisk together the eggs and sugar until the mixture is light yellow in color, and the sugar is dissolved. About 3 minutes.

Stir the warm chocolate mixture into the egg mixture and whisk until combined.

Sift in the flour, cocoa, and salt.

6.Preheat your oven to 425ºF (220ºC)

Pour the contents in the muffin tray with applying little butter to it(so that it doesnt stick at the bottom)

This should take between 11-15 minutes.

You'll know the cakes are done when the sides become firm while the centers are nice and soft.

If you bake them too much, then your "lava" won't flow.

The centers shouldn't be completely liquid-like, but they should still be soft. The tops should be puffed and a little bit cracked.