Heat a sauté pan on medium high heat. Add the butter and when melted, add in the flour. Using a spatula, mix until the flour absorbs all the butter. The result will be a paste like mixture. Next, you add your liquid in a little at a time. The liquid should be room temperature or heated on a low temp if pulled from the fridge. As you add the liquid to the roux, make sure the initial liquid is fully absorbed before adding in more to your mixture. Keep adding the liquid until the roux becomes creamy. If the roux is runny, you have added to much liquid. Over time, you will learn the consistency you want in your roux. The roux should look creamy, not runny or to thick. Once the roux is complete, start adding your cheese a little at a time. When it is fully melted, add until all the cheese has been used. Happy cooking and I hope this tip helps you in your cooking. Serve and Enjoy!