Ingredients
- 225g unsalted butter
- 60g dark chocolate (around 70%), chopped
- 110g milk chocolate, chopped
- 42g Dutch-process cocoa powder
- 5 large eggs, room temperature
- 1 tablespoon vanilla extract
- 450g castor sugar
- 140g plain flour
- 1 teaspoon table salt
- 225g chocolate chips
Directions
- Preheat the oven to 180°C (160°C fan) and prepare 9x13in pan with nonstick baking spray and a parchment paper sling across the width of the pan.
- Add the butter and both chocolates to a medium bowl set over a pan of simmering water. Stir together with a silicone spatula until the butter and chocolate have melted. Once melted, remove from the heat and immediately mix in the cocoa powder.
- Add the eggs, vanilla, and superfine sugar to a mixing bowl. Whisk together on medium speed until lightened in color and nearly tripled in volume.
- Add the chocolate mixture to the sugar and eggs and mix until combined.
- Switch to the paddle attachment and add the flour and salt. Mix until nearly all of the way incorporated.
- Stop the mixer and add the chocolate chips. Mix until fully combined and no streaks of dry flour remain.
- Smooth out in the prepared pan and bake for 25 to 30 minutes or until a toothpick inserted in the center comes out with streaks of thick batter (the toothpick should not come out clean nor should it come out entirely coated with shiny, wet batter).
- Remove from the oven and set the pan on a baking rack to cool completely.
- Once cool, lift out using the parchment paper sling and cut into squares.