In a large bowl, add the mascarpone cheese and beat until smooth.
In another bowl, whisk together the egg yolks and sugar then pour it into the cheese mixture while still whisking.
Add in the cocoa powder and vanilla extract then mix well.
Dissolve the instant coffee granules in water then add it to the mixture as well.
Cover and refrigerate for at least an hour but preferably overnight. Whip up some heavy cream if you like your tiramisu with a bit more of a fluffy texture.
Assemble the tiramisu by layering the ladyfingers, mascarpone mixture and whipped cream in glasses or serving dishes. Dust with cocoa powder before serving if desired.