Place the butter in a light-colored saucepan over medium heat and let it melt completely. Keep stirring gently as it begins to foam. After a few minutes, you’ll notice golden brown bits forming at the bottom and a rich, nutty aroma developing—this is the perfect stage. As soon as it turns a deep golden color (not dark brown), remove it from the heat immediately to avoid burning. Transfer it to a bowl and allow it to cool completely to room temperature before using.

In a large mixing bowl, add the cooled brown butter along with the brown sugar, white sugar, and vanilla extract. Using a whisk or an electric mixer, beat everything together until the mixture becomes smooth, creamy, and slightly thick. This step helps dissolve the sugar and creates a better cookie texture.

Add the eggs one at a time, mixing well after each addition. Continue whisking until the mixture looks glossy, slightly fluffy, and fully combined. This step is important for creating that soft, chewy center in your cookies.

In a separate bowl, combine the flour, protein powder, baking soda, and baking powder. Mix thoroughly so everything is evenly distributed. This prevents clumps and ensures the cookies rise properly.

Gradually add the dry ingredients into the wet mixture in batches. Use a spatula or mixer on low speed to gently combine. Stop mixing as soon as no dry streaks remain—overmixing at this stage can make the cookies dense and tough.

Add milk one tablespoon at a time, gently mixing after each addition until the dough becomes soft, smooth, and scoopable. The dough should hold its shape but not feel dry or crumbly. Adjust carefully—too much liquid will make the cookies spread too much.

Fold in the milk chocolate chips and dark chocolate chunks using a spatula. Distribute them evenly throughout the dough so every cookie has a mix of both chocolates. Avoid overmixing—just fold until combined.

Cover the dough and let it rest at room temperature for 20–30 minutes. This allows the flour and protein powder to fully hydrate, resulting in a softer dough and better final texture after baking.

Line a baking tray with parchment paper. Scoop approximately 70g portions of dough using a cookie scoop or your hands, and place them onto the tray. Leave enough space between each cookie to allow for spreading during baking.

Preheat your oven to 180°C (350°F). Place the tray in the center rack and bake for 10–12 minutes. The edges should be lightly golden and set, while the centers may still look slightly soft—this is ideal for achieving a chewy texture.

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