For the chestnut chocolate sponges, cream the butter with the sugar until fluffy. Fold in the chestnut puree and stir until smooth. Melt the chocolate in a water bath.
Stir the chocolate into the buttercream, flavor with the Baileys. Pour the mixture into a muffin tin lined with paper cups and let it set in the refrigerator for 5-6 hours, preferably overnight.
Cream the mascarpone, crème fraîche and sugar and pipe onto the chestnut chocolate sponges with a piping bag, garnish with a glazed chestnut.