1. Preheat oven to 325°F. Stir unsweetened chocolate and butter in heavy large saucepan over low heat until melted and smooth. Cool 5 minutes.
2. Mix in sugar, cinnamon, and salt. Add eggs, 1 at a time, then vanilla stirring until batter is smooth. Add flour until blended. Stir in chocolate chips.
3. Pour batter into greased 9x9 pan. Bake at 325° until tester inserted into center comes out with a few moist crumbs attached, about 35 minutes. Cool completely in pan on rack.
For brown sugar topping:
Combine sugar, cream and butter in heavy small saucepan over low heat until mixture is smooth and just starting to boil. Remove from heat; mix in vanilla. Allow to cool 5-10 minutes. Whisk until thick enough to spread. Spread over brownie. Allow to stand until topping sets.