4 ounces semisweet chocolate, chopped
1/2 cup (1 stick) unsalted butter
1 1/4 cups packed golden brown sugar
1 tablespoon ground cinnamon
1/4 teaspoon salt
3 large eggs
1 teaspoon vanilla extract
3/4 cup all-purpose flour
1 cup milk chocolate chips (about 6 ounce)
Brown Sugar Topping (recipe follows)

Preheat oven to 325 degrees F. Grease a 9-inch square baking dish.

Stir unsweetened chocolate and butter in heavy large saucepan over low heat until melted and smooth. Cool 5 minutes.

Mix in sugar, cinnamon, and salt. Add eggs, 1 at a time, then vanilla extract, stirring until batter is smooth. Add flour until blended. Stir in chocolate chips. Pour batter into prepared dish. Bake until a wooden pick inserted into center comes out with a few moist crumbs attached, about 35 minutes. Cool completely in pan on rack.

Brown Sugar Topping
1 cup packed golden brown sugar
1/4 cup whipping cream
1 tablespoon unsalted butter
3/4 tablespoon vanilla extract

Combine sugar, cream and butter in heavy small saucepan over low heat until mixture is smooth and just starting to boil. Remove from heat; stir in vanilla extract. Allow to cool for 5 to 10 minutes. Whisk until thick enough to spread. Spread over brownie. Allow to stand until topping sets.