In a small saucepan set over medium-high heat, bring milk, cream & sugar to a simmer together, heating just until bubbles appear Around the edges of the liquid.
Remove the pan from the heat and add the coarsely chopped bittersweet chocolate, stirring to melt it completely.
If necessary return the pan to low heat while stirring constantly with a wooden spoon until the chocolate is melted.
Mixture should appear smooth, evenly colored and very warm.
Serve warm in demitasse or espresso coffee cups with softly whipped cream and a shake of cinnamon if desired.
Serves 4.