Preheat your oven to 350 degrees and spray a 9x13 glass pan with nonstick cooking spray.
In a large mixing bowl, use a hand mixer to mix together melted butter, melted chocolate, and sugar.
Add in the eggs, and vanilla and mix until combined.
Add in salt, baking powder, and flour and mix until just combined.
Pour the brownie batter into the prepared pan and bake for 30 minutes. Remove from oven when done. Serve warm or store at room temperature.
Video
Notes
Only have cocoa powder? No problem!
Simply increase the amount of butter to 1 cup (16 tablespoons) and use 1 1/4 cups of cocoa powder in place of the baking chocolate. NOTE: 9x9-inch, 8x8-inch, or 11x7-inch pans produce thicker brownies and require a 45-50 minute baking time.