Place the butter in a light-colored saucepan over medium heat and allow it to 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 exactly what you want. As soon as the butter turns a deep golden color (not dark brown), remove it from the heat immediately to prevent burning. Pour it into a heat-safe bowl and let it cool fully 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 electric mixer, blend everything together until the mixture becomes smooth, creamy, and slightly thick. Take your time here—proper mixing helps dissolve the sugar and improves the final cookie texture.

Crack in the eggs one at a time, mixing well after each addition. Continue whisking until the mixture turns glossy, slightly fluffy, and well combined. This step helps create that soft, chewy center in your cookies.

In a separate bowl, combine the flour, protein powder, baking soda, and baking powder. Mix these dry ingredients thoroughly so the leavening agents and protein are evenly distributed. This prevents uneven rising and avoids clumps in your dough.

Gradually add the dry ingredients into the wet mixture in batches. Use a spatula or mixer on low speed to gently combine everything. Avoid overmixing—stop as soon as no dry streaks remain. Overmixing can lead to dense or tough cookies.

Add milk one tablespoon at a time, mixing gently after each addition, until the dough becomes soft, slightly thick, and scoopable. It should not be too dry or crumbly, but also not sticky like batter. Adjust carefully—this step balances the moisture lost from protein powder.

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

Line a baking tray with parchment paper. Using a cookie scoop or your hands, portion out approximately 70g of dough per cookie and place them on the tray, leaving enough space between each one to allow for spreading during baking.

Preheat your oven to 180°C (350°F). Place the tray in the center rack and bake the cookies for 10–12 minutes. The edges should look set and lightly golden, while the centers may still appear slightly soft—this is ideal for 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 allows them to firm up slightly while keeping the inside soft and tender. Serve warm for the best flavor and texture.