Coarsely chop the chocolate blocks. Slit the vanilla pod lengthwise and scrape out the pulp. Boil 500 ml milk, vanilla pulp, vanilla pod and salt. Melt the chocolate blocks while stirring. Mix starch, sugar and cocoa with 100 ml milk until smooth and stir into the chocolate milk. Bring to the boil again. Remove the chocolate milk from the stove and add 3/4 of the mocha beans.
Pour the flummery into four moulds (150 ml content) rinsed with cold water. Leave to cool for about 4 hours. Whip the cream until stiff and allow the vanilla sugar to trickle in. Remove the flummery from the rim of the mould with a sharp knife and turn it out onto dessert plates. Sprinkle with the remaining mocha beans, add some cream and sprinkle with advocaat. Decorate with lemon balm