1. Preheat your oven to 350 F (175 C). Lightly grease an 8×8 inch baking pan with butter or cooking spray, then line it with parchment paper, leaving an overhang on two sides to easily lift the brownies out later.

2. In a large mixing bowl, melt the unsalted butter. Once melted, stir in the granulated sugar until well combined. The mixture should look slightly glossy and uniform.

3. Whisk in the eggs one at a time, ensuring each is fully incorporated before adding the next. Stir in the vanilla extract and the sourdough discard. Mix until the batter is smooth and the discard is fully integrated, which might take a minute or two.

4. In a separate medium bowl, whisk together the all-purpose flour, unsweetened cocoa powder, baking soda, and salt. Make sure there are no lumps of cocoa powder.

5. Gradually add the dry ingredient mixture to the wet ingredients, mixing only until just combined. Be careful not to overmix, as this can lead to tough brownies. A few streaks of flour are okay; they will disappear during baking.

6. Gently fold in the chocolate chips until they are evenly distributed throughout the batter.

7. Pour the batter into your prepared 8×8 inch baking pan and spread it evenly with a spatula. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with moist crumbs, but not wet batter. The edges should look set.

8. Remove the pan from the oven and let the brownies cool completely in the pan on a wire rack before lifting them out using the parchment paper overhang. This cooling step is crucial for achieving that signature fudgy texture. Once cooled, cut into squares and serve.