Cut butter into chunks and melt in a saucepan over medium heat. Sieve the flour into the melted butter, a little at a time, whisking constantly to make sure it is fully combined and that there are no lumps. Keep whisking until the mixture thickens, taking care not to burn it. For a creamy sauce, add vegetable stock and cream.
Roux is a combination of equal parts flour and fat , used to thicken a variety of soups, sauces, and gravies. The recipe for roux which we’ve provided you is what’s known as a white roux. Cooking the roux slightly longer will yield a dark roux, which offers a deeper, more distinctly nutty quality to dishes.