Tiramisu in a Personal Mug

Bring mascarpone to room temperature, smooth it with a spatula and set aside. Mix egg yolk with sugar and rum. Place over a broiler and mix it for about 7 - 10minutes when the mixture becomes 160-165F. Pour the mixture into mascarpone, and mix it reallwell. Break the lady fingers into half so it can fit into the mug. Soak the lady fingers into the coffee of your choice. Assemble one layer of lady finger and cover with a layer of mascarpone until it fills up the entire mug. Place in the fridge for an hour or overnight. When serving, dust with cacao powder.