Put milk, sugar, vanilla bean and glucose into a stewpan. Put the chocolate into a round-bottomed copper pan and melt it slowly on the stove. Meanwhile, heat the mixture in the stewpan, not letting it boil, since you merely want to melt the sugar and glucose. When completely melted, pour this mixture, bit by bit, into the chocolate, while stirring. When thoroughly mixed, cook at moderate heat, constantly stirring. Cook to the 'ball' stage. (To test the stage of cooking by finger, dip the thumb and index finger into cold water, then into the mixture, bringing the 2 fingers together and dipping them again into water. This should be done quickly to avoid burning. The mixture forms a ball that can be rolled with the tip of the fingers.) Remove from the fire, add the butter, mix well, and pour onto an oiled marble slab in an oiled, iron framework. Let cool and cut. Source : The Art of French Cooking Posted by: Rina de Jong