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 about 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, bakery-style texture.

Add the egg and vanilla extract to the bowl, then mix well until everything is fully combined. The mixture should look glossy and slightly thick with no streaks of egg remaining. This helps create structure while keeping the cookies soft in the center.

In a separate bowl, combine the flour, protein powder, baking soda, baking powder, and salt. Whisk thoroughly so all the ingredients are 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. Continue mixing just until everything comes together and no dry flour is visible. Avoid overmixing, as this can make the cookies dense instead of soft and chewy.

Add the Fruit Loop cereal and gently fold it into the dough using a spatula. Be careful not to crush the cereal too much—keeping some pieces intact helps maintain texture and gives those colorful bursts in every bite.

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 texture of the cookies.

While the dough is chilling, preheat your oven to 180°C (350°F) and 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 that 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.