Mix 1 tablespoon each of icing sugar and cornstarch. Oil the mould (approx. 20 x 20 cm) and dust it with the starch-powder sugar mix. Mix gelatine with cold water in a pot and let it swell for about 2 minutes. Sift 250 g icing sugar with cocoa into a large bowl. Then heat the gelatine while stirring and bring to the boil briefly. Immediately stir the gelatine into the icing sugar with the whisk of the mixer until the mixture is frothy and forms peaks. Smooth the mixture slightly in the mould and allow to dry.
Remove the marshmallow mixture from the mould. Cut out circles (approx. 4 cm Ø each) with an oiled cookie cutter. Mix lemon juice, 1 tablespoon water and icing sugar to a glaze. Dribble over the marshmallows. Sprinkle with colourful sugar pearls. Leave to dry.