Position rack in center of oven; preheat to 375 degrees F. Lightly coat two 10-ounce ramekins with cooking spray; coat the insides of each with 1 1/2 teaspoons sugar.
Place chocolate in a small microwave-safe bowl. Microwave on Medium, stirring every 20 seconds, until melted, 1 to 2 minutes. (Alternatively, see “No Microwave?” below.)
Whisk egg yolk and cream in a medium bowl until combined. Whisk in the chocolate until smooth, then whisk in flour and cinnamon until incorporated.
Beat egg whites and salt in a medium bowl with an electric mixer on high speed until soft peaks form. Beat in the remaining 2 tablespoons sugar in four additions, until stiff, glossy peaks form.
Using a rubber spatula, gently fold half the beaten whites into the chocolate mixture until fairly smooth; then gently fold this combined mixture back into the remaining egg whites until no white streaks remain. Divide between the prepared ramekins and place on a baking sheet. Bake until puffed and firm to the touch, 18 to 22 minutes. Dust with confectioners’ sugar, if desired. Serve immediately.
Equipment: Two 10-ounce ramekins
No Microwave? Place chopped chocolate in the top of a double boiler over hot, but not boiling water. Gently stir until almost melted. Remove from the heat and stir until the chocolate melts completely.
Cut Down on Dishes: A rimmed baking sheet is great for everything from roasting to catching accidental drips and spills. For effortless cleanup and to keep your baking sheets in tip-top shape, line them with a layer of foil before each use.