Preheat the oven to 350°F. Line an 8x8-inch metal baking pan with parchment paper. Combine chocolate and butter in a medium saucepan and cook over low heat, stirring frequently until melted and smooth. Remove from the heat, add molasses and let cool slightly. Combine the eggs, sugar, vanilla, baking powder, cocoa and salt in a large bowl and stir until just incorporated. Add the chocolate mixture and stir until combined. Add the flour and fold in until just incorporated. Pour the batter into the prepared pan, spreading it out and smoothing the top. Bake for 30 minutes, until the centre is set. Remove to a wire rack and let the brownies cool for at least 20 minutes. (Take them out of the oven a little earlier if you want them to be chewier.) Cut into 2-inch squares.