I would like to try and make a blonde roux so that I could make a veloute sauce... however my girlfriend is allergic to wheat so I can't use flour as the ingredient. I was wondering if it's possible to subsitute the flour with 1/2 the amount of cornstarch instead? If so, how does this effect the taste of the roux and the veloute sauce? Thanks so much in advance!

You can make the veloute with cornstarch, but use it in a slurry (dissolved in water rather than added to the butter). Cornstarch is too fine to bind well with butter. Alternatively, however, potato starch works well to make a roux. It has slightly less thickening power than flour, but will do the job. Both will not affect the taste of the veloute. If using cornstarch diluted in water, you can always add a bit of butter AFTER it has thickened for added flavor. Good question.

Thanks so much for the help! How do I make the slurry exactly. Is it equal parts water to cornstarch?

Yes it is about equal parts water to cornstarch. Here is more info in the Slurry Drill-down.

You could also use white rice or brown rice flour for either a blond or a dark roux using proportions much like regular flour. Or Potato starch as a slurry. Have fun and experiment.

I'm gluten and grain free and until now I used arrow root that was good but more liquid.

I would like to try the patato starch but do I need to mix with the butter?

Thanks for you help

The potato flour can be mixed with the butter but water would also work. Cheers!

Does it matter if you use all purpose flour or self rising flour to make your Roux?

You could use self-rising flour; however, it does contain added ingredients which may interfere with the thickening power. It is better to use all-purpose or even cake/pastry flour as these have a higher percentage of starch. Cheers!

I made Potato Leek soup for the first time and when finished we felt it wasn't thick enough. Is it ok to reheat the soup and either let it reduce or add a thickening agent such as slurry of corn starch, potato starch or something else. I'd experiment but want to ruin it by adding the wrong thing.

Just curious if you have reviewed the lesson on Starch-Based Thick Soups. There is a lot of great information in there that will walk you through the process of making these types of soups.

You can thicken the soup with a slurry or you could simmer/steam a couple of potatoes and blend them into the soup. Reducing, especially if you have already added dairy products, may cause them to split. Cheers!