Wrap your avocado in aluminum foil and place it on a baking sheet.

Bake in an oven preheated to 100°C for around 10 minutes (depending on the hardness of the animal).

Remove the avocado from the oven, let it cool then unwrap it. If all goes well, it will be perfectly ripe, firm and slightly creamy.

For the short scientific explanation: aluminum foil helps retain the ethylene gas produced by the avocado and responsible for ripening.