Getting Ready

Preheat oven to 350 ºF (180 ºC). Line a buttered 8" square baking pan with parchment paper, allowing it to hang over sides, then butter parchment. 

Making

Combine butter, chocolate, and cocoa in a heat-proof bowl set over a pan ofbarely simmering water. 

Stir until butter and chocolate are melted, then let cool slightly. 

In a separate bowl whisk together flour, baking powder, and salt. 

In the bowl of an electric mixer fitted with the whisk attachment combine sugar, eggs, and vanilla. Beat this on medium speed until pale and creamy.

With mixer on low speed, add the chocolate/butter mixture, and beat until combined. Slowly add the flour mixture, beating until well combined (scraping down sides of bowl as needed). 

Pour batter into prepared pan, smoothing top with a rubber spatula. 

Bake until a cake tester comes out with a few crumbs but is not wet - about 35 minutes. 

Let cool slightly in pan, then lift out with parchment overhang. 

Serving

Let cool completely before cutting into squares. Serve!