Ingredients
1 cup all-purpose flour
2 teaspoons baking powder
1 teaspoon salt
2/3 cup granulated sugar
6 tablespoons unsweetened cocoa powder (divided)
1/2 cup milk
1 teaspoon vanilla extract
2 tablespoons margarine (or butter), softened
1/2 cup chopped nuts (optional)
1 cup packed brown sugar
1 1/2 cups boiling water
Method
Preheat the oven to 350°F (175°C). Grease a 6-cup casserole or baking dish and set aside. Sift the flour, baking powder, salt, granulated sugar, and 2 tablespoons of the cocoa powder together three times to ensure a light, well-mixed dry base.
In a separate bowl, combine the milk, vanilla extract, and softened margarine. Add the dry ingredients to the wet mixture and beat until the batter is smooth and uniform. Gently fold in the chopped nuts, if using. Spread the batter evenly into the prepared casserole dish.
In a small bowl, mix the brown sugar with the remaining 4 tablespoons of cocoa powder until well blended. Sprinkle this brown sugar–cocoa mixture evenly over the surface of the batter. Carefully pour the boiling water over the top. Do not stir.
Bake in the preheated oven for about 50 minutes, or until the top is set and a toothpick inserted into the center comes out mostly clean. The boiling water will create a moist, saucy layer beneath the cake as it bakes.
Remove from the oven and let rest for a few minutes before serving. Spoon portions so that some of the syrupy sauce from the bottom comes with each serving. Serve warm, optionally with a scoop of ice cream or a dollop of whipped cream.