Place the butter in a light-colored saucepan over medium heat and allow it to melt completely. Stir continuously as it begins to foam, then keep cooking until it turns a deep golden color with tiny brown bits at the bottom and a rich, nutty aroma develops. Immediately remove it from the heat to avoid burning, pour it into a bowl, and let it cool completely to room temperature before using.

In a large mixing bowl, combine the cooled brown butter with the brown sugar, white sugar, and vanilla extract. Using a whisk or an electric mixer, beat the mixture for 2–3 minutes until it becomes smooth, creamy, and slightly fluffy. This step helps create the soft, bakery-style texture in your cookies.

Add the eggs one at a time, mixing well after each addition. Continue mixing until the batter becomes glossy, thick, and fully combined with no streaks of egg remaining. This helps build structure while keeping the cookies soft in the center.

In a separate bowl, whisk together the flour, protein powder, baking soda, and baking powder. Make sure everything is evenly distributed and there are no lumps, especially from the protein powder, as this ensures consistent texture.

Gradually add the dry ingredients into the wet mixture in batches, mixing gently with a spatula or on low speed if using a mixer. Mix just until the dough comes together and no dry flour is visible. Avoid overmixing, as this 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 easy to scoop. The dough should hold its shape but not feel dry or crumbly. Stop adding milk once you reach this consistency.

Fold in the chocolate candies using a spatula, distributing them evenly throughout the dough. Be gentle during this step to keep the dough light and prevent the candies from breaking.

Cover the dough and let it rest at room temperature or in the refrigerator for 20–30 minutes. This resting time allows the flour and protein powder to fully hydrate, resulting in a softer and more flavorful cookie.

Line a baking tray with parchment paper. Scoop portions of dough (about 50–70g each) using a cookie scoop or your hands, and place them onto the tray, leaving enough space between each portion to allow for spreading.

Preheat your oven to 180°C (350°F), then place the tray on the center rack and bake for 10–12 minutes. The edges should be lightly golden and set, while the centers will still look slightly soft—this is ideal 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.