Heat oven to 350°. Grease a 9-by-13-by-2-inch baking pan and set aside. In a small bowl, whisk or sift 1 cup of the flour, baking powder and salt, then set aside. In a medium saucepan, melt the butter and chocolate over very low heat, stirring until smooth, then set aside to cool. In a large bowl, combine the eggs, brown sugar and vanilla and blend well. Stir in the cooled chocolate mixture. Gradually add the flour mixture and stir until blended, then fold in 1/2 cup of the mini chocolate chips and pour the batter into the prepared pan.

In a medium bowl, combine the peanut butter, sugar, cinnamon, cream and the remaining 1 Tbsp. flour. The mixture will be stiff. Drop spoonfuls of the peanut butter mixture randomly over the brownie batter and drag a knife through it in a zigzag pattern to create a marbled effect. Sprinkle with the remaining 1/2 cup mini chocolate chips. Bake for 25 to 30 minutes, then remove from the oven and let cool completely before cutting.