Yes, you can use chocolate milk mix instead of cocoa powder. Chocolate milk mix is a combination of cocoa powder, sugar, and other flavorings, so it provides a more complex flavor profile than just cocoa powder alone. The sweetness, creaminess, and added flavors all contribute to a unique and delicious chocolate experience. Chocolate milk mix also has the benefit of being much easier to use in baking than cocoa powder. You must measure the amount needed and mix it into your recipe as directed. However, since chocolate milk mix contains both sugar and additional flavoring ingredients, it may not produce the same intense chocolate flavor that pure cocoa powder does.