Take the duplos out of the packaging and cut / crumble them as small as possible with a sharp knife. Mix the sugar and milk in a saucepan over medium heat. Add the duplo crumbs to the pot and mix with the hand blender (this will also crush the small crumbs).
As soon as the mixture has completely melted, add the cream and stir. Add the vodka if you like. For those who like little or no vodka taste in the liqueur: 140 ml of vodka. For those who want to taste the alcohol in the liqueur: 160 ml or more. Fill the liqueur into a bottle and chill in the refrigerator for several hours.
One serving corresponds to a liquid amount of about 0.7 liters.