Whip the heavy cream in a bowl with a handheld electric mixer until it holds stiff peaks. Set in the fridge.
In a large bowl, cream together the mascarpone, sugar, vanilla and 1 1/2 tablespoons amaretto, by hand, using a spatula or wooden spoon. Fold in the whipped cream and set aside.
Add the coffee and remaining 1 1/2 tablespoons amaretto to a shallow bowl and set aside.
Dip 2 of the ladyfinger halves in the coffee mixture and lay them in the bottom of a 4-ounce glass. Spoon some of the cream mixture over them, sprinkle with some cocoa powder and repeat with another layer of dipped cookie halves, cream and cocoa powder. Repeat the same process with the remaining ingredients in another glass, cover with some plastic wrap and pop them in the fridge to set for a few hours.
When ready to serve, sprinkle the tiramisu with the broken amaretti cookies and a little extra cocoa powder.