Roughly chop the chocolate. Bring the cream in a small pot briefly to the boil, remove from the hotplate and melt the chocolate in it while stirring. Let the chocolate cream cool down at room temperature for about 2 hours. Cream butter and icing sugar with the whisk of the hand mixer. Add the chocolate cream by the spoonful and stir in. Put the butter-truffle mixture into a piping bag with a medium sized nozzle.
Pour the mixture into the hollow spheres to just below the rim. If necessary, carefully push the filled balls onto the work surface and spray some more mixture. Put the balls in a cool place overnight. Roughly chop the whole milk couverture and melt it on a hot water bath. Put the couverture in a disposable piping bag and cut off a small corner. Seal the balls with couverture and refrigerate for another 15 minutes. Coarsely chop the dark chocolate coating and melt it on a hot water bath. Let the chocolate coating cool down and warm it up again. Dip the balls briefly into the chocolate coating using a fork or praline utensils. Wipe off excess couverture at the edge of the bowl and place the balls on a praline rack to drain for about 5 minutes. Then turn the still moist balls into chocolate shavings and place them back on a grid. Chill for about 1 hour.
Let the chocolate coating cool down and warm it up again. Dip the balls briefly into the chocolate coating using a fork or praline utensils. Wipe off excess couverture at the edge of the bowl and place the balls on a praline rack to drain for about 5 minutes. Then turn the still moist balls into chocolate shavings and place them back on a grid. Chill for about 1 hour. Dust the butter-chocolate truffles with cocoa shortly before serving. Place in chocolate cups. Store in a cool place - but do not serve too cold