Arrange the individual tart tins on a small tray and set aside.
First, prepare the tart cases.
Melt the butter and Nutella in a large saucepan over a low heat, stirring occasionally.
Blitz the cookies in a food processor, or seal in a food bag and bash with a rolling pin, until you have fine crumbs.
Tip into the melted Nutella mixture and stir to coat evenly.
Divide the crumbs equally between the tart tins (allow just under 100g each).
Press them firmly into the base and up the sides of the tins, cover with cling film and chill in the fridge for about 15 minutes until firm.
Meanwhile, prepare the filling. Snap the chocolate into a large heatproof bowl and pour over the cream, vanilla extract and coffee liqueur (if using).
Either melt the chocolate in the microwave
in 30-second blasts, stirring between each go, or over a pan of simmering water, shallow enough that the water doesn’t touch the bowl.
When the chocolate is melted, stir the mixture until smooth and well blended.
Transfer the filling to a jug, leave to cool a little and then pour it into the set tart cases, dividing evenly so it comes just to the top.
Return to the fridge for 15-20 minutes until the filling is just beginning to set.
Then, sit five cherries with stalks upright into the centre of each tart.
They should settle into the pillowy chocolate.
Return to the fridge for a further hour or until completely set.
When ready to serve, softly whip the cream and serve in a small bowl.
Leave the tarts in the tins to serve or carefully remove and sit each one on a doily on a small plate.