Can somebody please tell me what it's called when you mix equal parts butter and flour to be added near the end of the cooking time to thicken a sauce? I want to know the name of the mixture. I've used it for 30 years or more, but never knew what it was called. I need to know what it's called so I can type up a recipe that uses it. I tried searching it, but I keep getting 'roux' and I know that's not right.