Put mascarpone and sugar in a large bowl. Whisk until the ingredients have completely combined.
Get your serving dish ready (around 12cm deep). Put the coffee into a shallow dish and dip in lady fingers for a few seconds until they are soaked, but not soggy. Layer them into the dish until you have used half the lady fingers. Spread half of the mascarpone over the cookies, sprinkle with chocolate. Repeat finishing with the mascarpone layer.
Cover with a clingfilm and chill overnight. To serve, dust with cocoa powder and sprinkle with chopped walnuts.
GF – make sure the ingredient doesn’t contain traces of gluten!