Roasting mushrooms and onions -Seeking Advice # updated#

[irisblue]

Last edited Mon Oct 1, 2018, 06:32 PM - Edit history (1)

I'd like to try roasting onions & mushrooms-big portabellas, button & crimini, then using that as the base for a cream of mushroom soup. Google has lots of recipes, but 350/20ish min, stirring seems too high a temp.
Any advice would be appreciated.

[randr]

1. I always do a slow long saute in oil/butter mix to bring out the sweetness

[irisblue]

2. Oven temp? 300? 350?

[Dr Hobbitstein]

3. They tend to dry out in the oven.

Pan roasting is superior, IMHO. Get a good sear.

[Polly Hennessey]

4. Everything I have ever seen

says 375 to 450 for 20 minutes. I’m with you that seems high. I can see them shriveling up and the onions burning. I agree that it might be better to slow-sauté them bringing out the natural sweetness of the onions and mushrooms.

[dem in texas]

5. Saute the whole shootin' match

Saute both onions and mushrooms in butter plus a little oil - the oil keeps the butter from burning. Stir until just starting to brown (a little seasoning - S & P, would be good) and you will have great base to work with for your soup. This will develop a good taste from all ingredients, onions, mushrooms and butter.

[Major Nikon]

6. It depends on what effect you're after

Browning can and does occur around 300F and higher. Carmelization requires at least 340F. So if you want to carmelize the sugars, you’ll need a minimum of 340F with higher temps resulting in shorter roast times. In order for the onions to reach those temperatures, much of their moisture must evaporate so you may want to slice or chop them first. The same is true for mushrooms. They won’t really start to brown until they give up some moisture.

Personally when making onion or mushroom based soup, I sauté them, but I can think of no reason why roasting won’t work.

[irisblue]

7. Update-irisblues' test kitchen

using 3 large portabella caps, I roasted each cap in 1 Tablespoon of butter, 40 minutes total, flipping every 10 min. Temp used were 250-350-400.( I used a oven thermometer to check the levels) the 3rd one, the 400 degree one was dried out the onions, the browned bits , when I tried to deglaze the pan, it was bitter.

For me the 350 degree cap would make the best roast veggie sandwich.
I will use a saute pan for the button mushrooms.

In the crockpot now is this recipe

https://www.allrecipes.com/recipe/22890/creamy-mushroom-soup/ but I used button mushrooms instead of shitake.