Print How To Make A Roux A roux is flour and butter cooked together to create a thick sauce. It is whisked over heat until smooth to your desired darkness. Learn how to create a white roux, also known as Béchamel sauce. Get Started Step 1: Melt butter over medium heat. Step 2: Add equal parts flour to the melted butter. Step 3: Whisk to incorporate flour and cook evenly until smooth. Step 4: Continue whisking until roux becomes a light golden brown color Step 5: Add seasoning and serve on top of completed dish.