Preparation
1. Heat the oven to 350*. Lightly coat an 8-inch square pan with cooking spray. In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt. Set the mixture aside.
2.Heat the butter in a small saucepan until just melted, being careful not to burn it. Remove the pan from the heat. Add the chopped chocolate, stirring until it is melted. Let the chocolate cool until it's tepid.