I am trying to come up with some kind of mousse, based on mushrooms, to be put on top of slices of potatoes just out of the deep-fryer. One of the main difficulties I'm facing is that my attempts tend to "melt" when exposed to the heat of the potato slice. I had a few first attempts, with
- a béchamel-like cream, cooked with a roux with a rather firm texture; it turns out a bit too thick and is not as pleasant as a lighter mousse;
- a whipped-cream base: cook the mushrooms in cream, cool it down, blend it and whip it. The texture is not optimal, and it "melts" quite quickly when exposed to heat;
- I thought of some method based on starch, but didn't try it yet;
- I also thought of adding a bit of gelatin or agar-agar, but I'm not confident in the proportions to use here — I certainly don't want a jelly here. It should also remain vegetarian, so agar-agar is preferred.
What options seems most promising to you? Are there any other possibilities or tricks that I could use?