Slice 1 rib of chocolate (approx. 15 g) with a peeler into shavings and set aside. Break the rest of the chocolate into small pieces. Melt together with the butter in a hot water bath. Heat 50 g cream slightly, dissolve coffee powder in it and stir into the melted chocolate. Leave to cool at lukewarm temperature.
Beat the egg whites with the whisks of the mixer until stiff, adding 30 g icing sugar. Carefully fold 2 portions of beaten egg whites into the melted chocolate. Divide the chocolate mixture into four glasses (each containing approx. 250 ml). Freeze for at least 3 hours, preferably overnight.
Let the chocolate coffee ice cream thaw for about 5 minutes before serving. Whip 100 g cream until semi-stiff and add 30 g icing sugar. Spread the cream on the ice cream in the glasses and sprinkle with the chocolate shavings.