Heat the cream, zest, and cinnamon in a saucepan to boiling. Remove from the heat and let steep 2 hours.
Heat the chocolate in a small heavy pan over low heat until melted. Continue cooking, stirring constantly, until it is “scorched” and thick, about 3 minutes. Transfer to a large mixing bowl.
Strain the cream into another saucepan and reheat to boiling. Whisk the egg yolks and
Strain the custard into the chocolate and stir until smooth. Strain again. Place in a larger bowl filled with ice water and chill the custard well. Freeze in an ice cream machine according to the manufacturer’s instructions.