1 1/4 cup all-purpose flour
1/2 cup regular cocoa powder
1 tsp baking soda
½ tsp salt
½ baking powder
1 cup sugar
½ cup dark brown sugar, packed
½ cup unsalted butter, room temperature
1 ¼ cup buttermilk, room temperature
2 large eggs, room temperature
1 tsp vanilla extract
170 g chocolate, chopped, melted, cooled
Preheat oven to 350F (175 C). Grease and line the baking tin with parchment paper.
Sift flour, cocoa, baking soda, salt and baking powder into a large bowl (or into the bowl of a standup mixer fitted with the paddle attachment). Add sugars and butter and blend until a crumbly texture.
In a small bowl, whisk buttermilk, eggs and vanilla together and add to the larger bowl while mixing at low speed. Once incorporated, increase speed to medium-high and blend until smooth, about 3 minutes.
Slowly pour in melted chocolate until evenly blended, then scrape batter into the prepared baking tin and tap it a few times on the counter to remove any trapped air in the batter.
Bake cake for 40 to 50 minutes, until a tester inserted in the centre of the cake, comes out clean. Cool cakes for 30 minutes in the pan, then carefully turn out onto a cooling rack to cool completely.