Place chestnuts in a food processor and process until fine. In a bowl, whisk the egg yolks and sugar until thick and creamy.
Whisk in the processed chestnut and half the brandy (or marsala).
Fold through the mascarpone being careful not to overbeat.
In a separate bowl, whisk the egg whites until stiff.
Beat one tablespoon of the whites through the mascarpone mixture then fold through the remainder.
Combine hot coffee remaining brandy (or marsala) in a shallow dish.
Leave to cool.
Dip Savoiardi biscuits into coffee mixture making sure they are soaked.
Place 4 Savoiardi pieces in the base of a 20cm - 22cm round dessert dish, or 1-2 in the base of a 250ml ‘café latte’ glass.
If using the dish, cover with half of the mascarpone and chestnut mixture, smoothing it evenly.
Sprinkle with grated chocolate.
Continue with another layer.
If using latte glasses, half fill each glass with chestnut mixture and layer as above.
Top with grated chocolate and sprinkle lightly with a few very fine coffee grains.
Cover with plastic wrap and leave to chill overnight in refrigerator.
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