Fennel Has it occurred to your DH that supermarkets sell mushrooms by the ton, any we do not have wholesale deaths by fungi?
I am another who uses them a lot, I have a whole host of non-meat rcipes teaming mushrooms with chestnuts etc and use them in all kinds of casseroles, stews, riottos, pasta dishes. You name it and I will put mushrooms in it
If your DH is wary about them, I do not think I would start by giving him dishes based on mushrooms to begin with, but put some in casseroles, stews, stuffings etc and as he gets used to them, start to do dishes in which they feature more. Like a mushroom risotto, as part of a vegetable mix. Lots on recipes online and only then move on to dishes where they star, stuffed mushrooms, mushroom omelettes and mushrooms on toast.
For mushrooms on toast, I slice and simmer the mushrooms in a little water and then stir in a couple of spoonsful of quark(or double cream, or pain fromaage fraiche, possibly creme fraiche), just before serving and reheat gently.