For the base, grease a tart mould with a lifting base (26 cm Ø) well. Twist the biscuits apart, scrape the cream into a pot. Add 60 g butter and melt carefully. Finely grind the biscuits in the universal chopper. Mix butter mix and biscuit crumbs. Press into the mould as a flat base, pulling up at the edge. Chill for about 1 hour.
Wash the cherries, remove the stalks, remove stones and drain. For the mousse, whip 400 g cream until stiff. Coarsely chop the chocolate coating. Warm milk in a pot at low heat, dissolve chocolate coating in it while stirring. Pour the chocolate milk into a bowl and let it cool down for about 10 minutes. Fold in cream in portions, then fold in cherries. Pour the chocolate-cherry mousse into the mould, spread evenly and chill for about 2 hours.
For the topping, whip 200 g of cream until stiff, allowing the cream stiffener to trickle in. Remove the tart base from the mould and place on a cake plate. Spread the cream loosely on the tart and dust with baking cocoa.