Line an 8x8-inch baking pan with parchment paper, leaving some overhang on the sides for easy removal. Lightly grease the paper to prevent sticking. Preheat your oven to 350°F (175°C).

In a heatproof bowl, combine unsalted butter and chopped dark chocolate. Melt them together using a double boiler or microwave in 20-second intervals, stirring in between. Once smooth, mix in the cocoa powder to enhance the chocolate flavor. Let the mixture cool slightly.

In a separate large bowl, combine granulated sugar and brown sugar. Add eggs one at a time, whisking until the mixture is thick and slightly pale. This step helps create a crackly top on the brownies. Stir in the vanilla extract.

Add sourdough discard to the sugar mixture and whisk until fully combined. The discard not only enhances the texture but also helps balance the sweetness with a slight tang.

Gently fold the melted chocolate mixture into the batter. Then, sift together the flour, baking powder, and salt before gently incorporating them into the batter. Mix just until no streaks remain—overmixing can affect the texture. If adding chocolate chips, fold them in at this stage.

Transfer the mixture into the lined baking pan, smoothing the top for even baking. Bake for about 28–32 minutes, or until the edges are set and a toothpick inserted in the center shows a few sticky crumbs.

Let the brownies cool in the pan for at least 20-30 minutes before lifting them out using the parchment paper overhang. For neat slices, use a sharp knife and clean it between each cut.