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 watch closely as it turns golden with small brown bits forming at the bottom. You’ll notice a rich, nutty aroma—this is when it’s ready. Immediately remove it from the heat to prevent burning, pour it into a heat-safe 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, vanilla extract, and miso paste. Using a whisk or electric mixer, mix until the mixture becomes smooth, creamy, and fully combined. Make sure the miso is evenly incorporated so there are no lumps—this ensures a balanced flavor throughout the cookies.

Add the eggs one at a time, mixing well after each addition. Continue mixing until the mixture becomes glossy, slightly thick, and well emulsified. This step helps create structure while keeping the cookies soft and chewy.

In a separate bowl, combine the flour, protein powder, baking soda, and baking powder. Whisk thoroughly to ensure everything is evenly distributed and there are no clumps, especially from the protein powder.

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. Be careful not to add too much milk, as it can cause excessive spreading during baking.

Fold in the chocolate chunks using a spatula, making sure they are evenly distributed throughout the dough. Keep the folding gentle to maintain a soft dough texture.

Cover the dough and let it rest at room temperature for 20–30 minutes. This allows the flour and protein powder to fully hydrate, improving the texture and making the cookies softer after baking.

Line a baking tray with parchment paper. Scoop portions of dough (about 60–70g each) 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 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, bakery-style texture.

Remove the cookies from the oven and allow them to 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.