Prepare the dough: In a large mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until smooth and fluffy. This usually takes about 2–3 minutes with a hand mixer. Beat in the eggs one at a time, making sure each is fully incorporated before adding the next. Stir in the vanilla extract for flavor.
Mix the dry ingredients: In another bowl, whisk together the flour, baking soda, salt, and cocoa powder until evenly combined. This ensures the cocoa distributes well and the cookies bake with an even chocolate flavor.
Combine wet and dry mixtures: Gradually add the dry mixture to the butter mixture, mixing slowly to avoid flour spilling out. Once combined, fold in all three chocolates—semisweet chips, white chocolate chips, and milk chocolate chunks—making sure they’re spread throughout the dough. The mixture will be thick and loaded with chocolate pieces.
Chill the dough (optional but recommended): For extra chewy cookies, cover the bowl with plastic wrap and refrigerate the dough for 30 minutes. This helps the cookies hold their shape while baking.
Bake the cookies: Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper. Scoop out about 2 tablespoons of dough per cookie, roll gently into a ball, and place on the sheet about 2 inches apart. Bake for 10–12 minutes until the edges are set but the centers still look slightly soft.
Cool and serve: Allow cookies to rest on the baking sheet for 5 minutes before transferring them to a wire rack. This helps them finish setting without overbaking. Serve warm for gooey melted chocolate centers or at room temperature for a firmer bite.
