Bring the heavy cream to a boil in a saucepan, then pour over the chocolate in a heat-safe bowl
Cover for 5 minutes, then stir until the chocolate melts and a smooth, shiny ganache forms
Whisk the chilled heavy cream, sugar and vanilla in a bowl until the cream becomes thick
Add the mascarpone cheese in 2-3 additions and mix on low speed until combined. Adjust the amount of mascarpone cheese based on your preference of taste and thickness
Mix the cocoa powder in the cooled espresso (or strong coffee) and place in a deep plate
Dip the ladyfingers into the espresso one at a time, for ~2 seconds per side, and arrange tightly in the bottom of a 9x9" pan / dish
Cover with half of the mascarpone cream and spread using an offset spatula
Pour over half of the ganache and spread it
Repeat the process, creating another layer of ladyfingers, mascarpone cream and ganache
Cover and place the Chocolate Tiramisu in the fridge for at least 4 hours, ideally overnight
Dust with more cocoa powder right before serving
