From the Phase I food list
SWEET TREATS (Limit to 75-100 calories per day)
Chocolate powder, no-added-sugar
Chocolate syrup sugar free
Cocoa powder, baking type
Better check the calories in the chocolate. A half bar of that chocolate is 180 calories and I see Maltitol and Chocolate Liquor, Malitol can give you digestive problems if too much is eaten and it IS the first ingredient. 35% of the fat is saturated as well so this is probably not for Phase I.
Perhaps you can mess around with the recipe some more and try SF cocoa powder or SF chocolate syrup.