Place chopped chocolate in a mixing bowl; set aside.
Simmer milk over medium-low heat in a heavy saucepan. Whisk in cocoa, orange peel and cinnamon. Add vanilla bean; return to a simmer and continue to cook for 3 minutes. Stir a small amount of the hot milk into egg mixture, then combine eggs with hot milk. Continue to cook on low heat until custard lightly coats back of spoon, stirring constantly. Remove from heat; strain to remove orange peel and vanilla bean. Set aside.
Slit vanilla bean lengthwise and scrape seeds into cream. Heat cream in a heavy saucepan over medium-low heat to a simmer. Remove from heat and pour hot cream over chopped chocolate; stir until chocolate is melted and mixture is smooth. Add custard mixture. Cover and refrigerate several hours or overnight.
Prepare ice cream in a 1-1/2 quart ice cream machine according to manufacturer's instructions.
Tips & Tricks
For Chocolate Peppermint Truffle Ice Cream, substitute 1/3 cup crushed peppermint candy for the orange peel and cinnamon. Do not strain custard, simply remove vanilla bean.