Break chocolate into pieces. Melt with fat in a hot water bath. Lift it out and let it cool down for about 15 minutes at room temperature. Whip cream with icing sugar and cocoa until creamy. Add two portions to the chocolate mixture.
Chill for about 20 minutes, stirring frequently.
Place a piece of cling film (approx. 30 x 60 cm) on a piece of aluminium foil of the same size. Fold marshmallows under the chocolate mixture. Spread the mixture over the front third of a long side in such a way that an approx. 15 cm wide edge remains free on the left and right.
With the help of the foils like a candy to a roll (approx. 5 cm Ø); screw in firmly. Keep cold for approx. 3 hours.
Meanwhile roast the nuts in a pan without fat for about 1 minute. Sprinkle with sugar. Caramelise while turning until golden brown. Spread on a piece of baking paper and let it cool down. Finely chop the nuts in a universal chopper or with a knife.
unwrap the chocolate roll. Leave to soften for about 15 minutes at room temperature. Spread the nuts on a baking tray and roll the roll in it. Cut into slices.