Preheat oven to 425° 

Remove middle rack from oven; place lower rack in the lowest setting.

Coat 6 (8-ounce) soufflé dishes with softened butter. Divide 2 1/2 tablespoons sugar and sprinkle in bottoms of dishes; set aside.

 Stir together the cornstarch and milk in a heavy pan; place over medium-high heat and cook, stirring constantly, until smooth. Move the pan off the heat and add the chocolate pieces, 2 tablespoons butter, and 3 tablespoons sugar. Stir until the butter and chocolate are melted, moving the pan back over low heat if necessary. Remove from the heat and cool to room temperature.  When cooled, stir in the egg yolks one at a time; stir in vanilla and salt.

Place egg whites in a large mixing bowl; beat at high speed with a mixer until stiff, glossy peaks form, taking care not to overbeat. Gently fold one-fourth of egg whites into chocolate mixture to thin; gently fold this mixture into remaining egg white mixture. 

Gently spoon mixture into prepared soufflé dishes. Tap dishes on countertop to level; evenly distribute dishes on a baking sheet and place on the bottom rack of oven. Immediately reduce oven temperature to 350° (do not remove soufflés from oven). Bake 25 minutes for a soft center or 30 - 35 minutes for a solid center.

Meanwhile, prepare sauce: heat cream in a heavy saucepan until hot but not boiling; add chocolate pieces and cook over low heat until chocolate is melted and sauce is smooth. Stir in cayenne pepper if desired; keep warm until needed. Sauce will harden when cooled; reheat over low heat or in microwave.

Serve soufflés at once with Cayenne Chocolate Ganache.