Cut 1 läckerli per person in half diagonally, set aside for garnish. Quarter the remaining Läckerli, pour over the milk and soak for about half an hour with the lid closed. Finely purée with a hand mixer, set aside.
Put the chocolate in a suitable bowl, place in a not too hot water bath and stir until melted. Add Grand Marnier, stir until smooth, stir into the liqueur mixture.
Melt the gelatine with the boiling water, mix with 2 tablespoons of läckerlime mixture and stir well into the rest of the mixture on the spot. Cool until the mixture is slightly firm at the edges, stir until smooth.
Fold in whipped cream, refrigerate mousse with lid closed for about 1 1/2 hours.
Serve: cut the mousse exactly with two spoons, arrange on plates, garnish with the lollipops put aside.
Tip: use orange juice instead of Grand Marnier.