Preheat the oven to 425 °F. To make removal of the cakes easy, grease 3 spots in a muffin tin (or 2 6-ounce ramekins) and sprinkle with cocoa powder.
In a microwave safe bowl, melt the chocolate and butter in 20 second increments, stirring un between each time until smooth.
Allow the chocolate mixture to cool for a minute or two (so that it doesn't cook the egg), then whisk in the egg and egg yolk until smooth.
Divide the mixture evenly between the 3 prepared spots in the muffin tin (or ramekins).
Bake for 7-9 minutes until the sides appear set (11-13 minutes for ramekins). The center will still look soft.
Let sit for one minute and then run a knife all the way around the edges of each lava cake to make them easy to release. Place a flat plate or cookie sheet upside down on top of the hot muffin tin, then use oven mitts and hold the two together and invert the muffin tin onto the plate. Remove the muffin tin and use a spatula to move the lava cakes to individual dishes.
Serve immediately, topped with ice cream, salted caramel and more as desired.
Notes
Make Ahead: This is a perfect dessert to prepare ahead! Prepare the lava cake batter and divide it into the muffin tin/ramekins. Then cover and refrigerate for up to 3 days until ready to bake. Or you can freeze the prepared tin for up to 3 months. Thaw in the fridge and bake as directed, adding an extra minute.To Store: If you have leftover easy chocolate lava cakes, cool to room temperature and then store in an airtight container in the refrigerator for up to 3 days or freeze for up to 3 months.To Reheat: You can rewarm this decadent dessert in the microwave for 20-30 seconds. This method of reheating takes less time but the center of the cake will end up cooking through. For better results, you can rewarm in the oven at 400 F for a baking time of 4-6 minutes.