Preheat the oven to 450° F. Place a rack in the middle of the oven.
Prepare a jumbo, 6-cup muffin tin OR a regular 12-cup muffin pan by oiling the muffin cups. Cut circles from parchment paper to line the bottom of each muffin cup. ALTERNATIVELY, you could bake and serve the lava cakes in individual ramekins without any parchment liners.
Melt the chocolate and butter together gently over very low heat, checking and stirring it frequently, until it is melted and smoothly combined. Remove it from the heat.
Meanwhile, beat the eggs at high speed for 3 to 5 minutes until they become light in colour and foamy with small bubbles on the surface.
Gently, stir the beaten eggs into the chocolate mixture one-third at a time.
Divide the batter among the prepared muffin cups, and bake until the centre reaches a temperature of 144° F (62° C), 5 to 10 minutes, depending on size. The centre should still be very soft.
Allow the cakes to cool in the pan until they are set just enough to remove without breaking, 5 to 10 minutes.
Invert a warm cake onto each serving plate, and drizzle Chocolate Ganache Icing over each one.
The finer you chop the chocolate and butter, the faster they will melt.
If you use a double boiler to melt your chocolate, be very careful not to get any water into the chocolate-butter mixture.
If you make smaller cakes in a regular muffin tin or small ramekins, they may cook faster.