185 gmbutter, coarsely chopped325 gmcaster sugar50 gmDutch-processed cocoa, sifted, plus extra to serve85 gmmarshmallows1½ tsppure vanilla essence190 mlevaporated milk375 gmdark chocolate (about 60% cocoa solids), finely chopped100 gmcandied violets, crushed with a mortar and pestle, plus extra to serve if desired (see note)
Melt butter in a saucepan over low heat, whisk in sugar and cocoa, then add marshmallows, vanilla essence and evaporated milk. Stir continuously until marshmallows melt (10-15 minutes), then strain through a fine sieve into a large bowl. Whisk in chocolate and when completely melted, add violets. Mix well and pour into a greased and baking paper-lined 15cm x 20cm cake pan or plastic container. Smooth top, cool to room temperature, then refrigerate until firm (about 2 hours). To serve, using a hot knife, cut into squares, dust with cocoa and serve.