Blitz the biscuits to fine crumbs, stir in the melted butter and divide between 8 serving glasses. Press the crumbs down lightly in the base.The glasses need to hold two layers of sponge fingers and 3 layers of cream, so they should be fairly tall.
Mascarpone cream
Put the mascarpone, cream cheese, whipping cream, icing sugar and vanilla sugar in a bowl and whisk to a soft, light cream. Take care not to over-whip it.
Spoon the mascarpone cream into a piping bag.
Tiramisu cheesecake in glasses
Dip all the sponge fingers in the espresso and set them aside on a chopping board.
Pipe a little mascarpone cream onto each biscuit base, snap a sponge finger in half and lay the 2 halves in each glass. Press them gently into the cream if needed.
Continue with the next layer of cream, another layer of sponge fingers, and finish with a layer of mascarpone cream on top.
Smooth the top with the back of a warm spoon and dust with cocoa powder, ideally just before serving.