Cut the dates lengthwise and remove the pit. Stir the marzipan mixture with rum until smooth and fill into a piping bag with an 8 mm diameter nozzle.
Pipe the marzipan mixture into the fruit. Refrigerate the filled dates for half an hour. Melt the white couverture and dip the dates in it, drain and place on parchment or baking paper. Refrigerate until the couverture is firm.
Place the dark chocolate coating in a freezer bag and heat in a water bath. Cut off a very small corner and, using quick motions, pipe the dark chocolate coating onto the white dates. Then refrigerate the dates again for 30 minutes until the chocolate coating is hard.