WHITE CHOCOLATE SAUCE: Place chocolate in a small bowl. Bring cream to a boil in heavy small sauce pan. Pour cream over chocolate, whisk until smooth.
CHOCOLATE SAUCE: In a small heavy saucepan combine the cream and the brown sugar, bring the mixture to a boil over moderately high heat, whisking occasionally. Once boiling, whisk until the brown sugar is dissolved. Remove pan from heat, add chocolates and whisk the mixture until they are melted. Whisk in butter and cinnamon until the sauce is smooth. Let the sauce cool slightly. The sauce may be made 1 week in advance and kept covered and chilled. Reheat the sauce over very low heat, stirring occasionally, until it is warm.