In a large mixing bowl, add the softened butter along with the brown sugar and white sugar. Using a whisk or an electric mixer, beat the mixture for 2–3 minutes until it becomes smooth, creamy, and slightly fluffy. This step is important because properly creaming the butter and sugar creates air pockets that help give your cookies a soft, tender texture.

Add the egg, vanilla extract, and sourdough discard to the bowl. Mix everything together until fully combined and the mixture looks glossy and slightly thick. Make sure there are no streaks of egg left and the sourdough is evenly incorporated for a consistent flavor throughout the dough.

In a separate bowl, combine the flour, protein powder, baking soda, baking powder, and salt. Whisk these dry ingredients thoroughly so that the leavening agents and protein powder are evenly distributed, preventing uneven rising or clumps in your cookies.

Gradually add the dry ingredients into the wet mixture in batches. Mix gently with a spatula or on low speed if using a mixer, just until everything comes together and no dry flour is visible. Avoid overmixing at this stage, as it can make the cookies dense instead of soft and chewy.

Add the chocolate chips and fold them into the dough using a spatula. Make sure they are evenly distributed so every cookie gets a good amount of chocolate in each bite. Keep the folding gentle to maintain a soft dough texture.

Cover the dough and place it in the refrigerator for 20–30 minutes. This chilling step helps firm up the dough, prevents excessive spreading during baking, and improves the overall flavor and texture of the cookies.

Preheat your oven to 180°C (350°F) while the dough is chilling. Line a baking tray with parchment paper to prevent sticking and ensure even baking.

Once the dough is chilled, scoop out portions of dough (about 50–70g each) using a cookie scoop or your hands, and place them onto the prepared baking tray. Leave enough space between each cookie to allow for spreading.

Place the tray in the preheated oven and bake for 12–15 minutes. The edges should turn lightly golden and set, while the centers may still look slightly soft—this is perfect for achieving a chewy texture.

Remove the cookies from the oven and let them rest on the baking tray for a few minutes before transferring them to a cooling rack. This allows them to firm up slightly while keeping the inside soft and tender. Serve warm for the best flavor and texture.