Traditionally, onions are slowly braised in butter before being drained, puréed and added to a pre-prepared Bechamel sauce to make Soubise sauce.

This seems a terrible waste of flavour, if you were to make the Bechamel last of all with the onion-flavoured butter, would this be too overpowering and would it ruin the final sauce?

(I'm assuming here that any water added to the butter during the braising/poaching process would not effect the thickening of the milk/cream and would have evaporated off).

  • 1
    Try it and see? So many folks make Soubise with cream instead of bechamel these days, there's no real guide on it.
    – FuzzyChef
    Apr 11, 2023 at 23:30

1 Answer 1


I don't know specifically about using the butter to make soubise, but you can certainly make a bechamel sauce from the butter used in the frying. I have done so many times - usually for use in a pasta based dishes such as "Mac and cheese".

The onion flavour is present, but not too strong and seems to be mostly retained in the onions themselves.

The water that boils out of the onions (and butter) has evaporated by the time the fat from the butter reaches the boiling point of the fat. As you can make bechamel from things like olive oil, the water content of the butter and/or onions isn't a huge consideration in the process anyway, unless you are removing the onions before they caramelize and are still losing water. At this point you could simply let the water boil off before adding the flour.

  • 5
    back when I could still eat dairy, I would sweat onions in butter, add flour and make a roux around the onions. And then use it for bechamel (for Mac and cheese, chicken a la king, etc). So slightly oniony béchamel should be fine.
    – Joe
    Apr 12, 2023 at 2:04
  • 2
    @Joe Yes, exactly what I would do too. Also works around bacon, chicken breast pieces and, I suspect, anything you might fry in oil or butter before making a bechamel as the sauce.
    – bob1
    Apr 12, 2023 at 2:49
  • 2
    Similarly, I make any & all 'sauces with a roux-type base' around what's already frying/sautéing in the pan (unless it's simply to big to work around). Works just the same, imparts all the flavours of what you were frying.
    – Tetsujin
    Apr 12, 2023 at 12:44
  • @bob1 AFAIK butter fat like most fats doesn't really have a boiling point - it has a smoke point instead. It will smoke and burn rather than boil.
    – bdsl
    Apr 12, 2023 at 13:36
  • @bdsl butter sort of does, as it’s about 11% water in American butters. That’s why you cook it until it stops foaming before adding the flour, and why some people make clarified butter or ghee to save a little time (although there are also other reasons for marking them)
    – Joe
    Apr 12, 2023 at 13:39

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