preheat the oven
generously butter a 10 inch springform pan, add a circle of parchment and butter it as well for the best results, set aside
heat a saucepan over medium heat
place a bowl over the warming water
chop up the butter and drop it in the bowl
while the butter melts rough chop the chocolate and add it to the bowl as well
don't let the chocolate get too hot, you'll want to remove it as it starts to melt and then stir it until it melts compeltely
meanwhile measure out the remaining ingredients if you haven't already
separate the eggs and be sure not to get any yolk in the whites
once the chocolate is melted set it aside and let it cool for about 5 - 10 minutes
meanwhile whip the egg whites until the form peaks, don't over beat them or they will be dry
whisk the sugar, espresso powder, salt, egg yolks and vanilla paste into the melted chocolate
once the egg whites are stiff use a large metal spoon to fold half the whites into the chocolate mixture
once incorporated fold in the remaining eggs whites
scrape into the prepared pan
bake in the preheated oven 30 minutes, don't open the oven to check on the cake it will deflate
remove the cake from the oven and let it rest on a wire rack for 10-15 minutes
then remove the ring and just let the cake cool
once chilled cut the cake in half with the leveler to make 2 thin cakes
stir the whipping cream, sugar, and vanilla in the bowl of a stand mixer
then whip it on medium until stiff peaks form, don't over whip it or you'll get butter
place one layer of the cake on a cake plate, top it with about half of the whipped cream
gently top with the remaining layer and the rest of the whipped cream
use a small cheese grater or zester to grate some of the chocolate over the whipped cream
chill until ready to serve, don't let chill more than 20-30 minutes or it will deflate