Prepare the basic chocolate sponge cake.

Overturn onto a sugared plate and pull off the parchment paper.

Cool the cake.

Then cut out 20 small sponge cake bases with a round cookie cutter.

Place the cake bases in appropriately sized small ring forms and brush with marmalade.

For the sour cherry filling, boil ¾ of the cherry juice with sugar.

Mix the rest of the juice with cornstarch and then stir into the boiling mixture.

Add cherries, stir briefly, and then remove from heat.

For the chocolate mousse, melt chocolate and mix with egg yolks, simple syrup, and heavy cream.

Add water to the gelatin and dissolve in slightly warmed rum.

Stir into the chocolate mixture.

Fold in the whipped cream.

Put the chocolate mousse into the forms and add the cherries (without juice) to the middle.

Chill for 2 hours.

Release the cooled tartlets from the rings with a knife dipped in hot water.

Cover the tartlets all around with sweetened whipped cream.

Pipe a ring on top.

Press the chestnut purée through a potato ricer or grater and place on top of each tartlet.

Finally, garnish each tartlet with a cherry.