Mix in a small sauce pan the milk, cream and vanilla. In a bowl add sugar to egg yolks and stir. Add a little of the milk mixture to the egg yolks and continue to stir. Gradually, fully blend the two mixtures. Place over medium heat and stir constantly. Before it boils, at about 84-85º C (beyond this temperature the cream will spoil because the yolks will cook), remove from heat and pour over the broken in pieces of cooking chocolate. Remove vanilla stick and put through the blender until it has become smooth. Allow it to cool down still stirring and fill 6 coffee cups. Keep refrigerated.