Line muffin tin cups with cling film and place in the freezer.
Whisk double cream to soft peaks, then whisk in condensed milk.
Fold in peppermint oil to taste.
Shave chocolate into the mix and fold in.
Scoop mixture into muffin cups, smooth tops, and freeze overnight.
Preheat oven to 180°C and line a tray with greaseproof paper.
Melt butter and chocolate in a bowl over simmering water.
Whisk sugar, eggs, and vanilla together, then fold in chocolate.
Sift flour, cocoa, and baking powder together and fold into mixture.
Place 36 tablespoons of batter on tray and bake for 6-8 minutes.
Cool biscuits on a wire rack.
Melt optional chocolate and pour over biscuits to cool.
Sandwich frozen ice cream discs between two biscuits.
Dust with cocoa and icing sugar before serving immediately.