I made this last night and it was amazing, I didn't really follow a recipe but did check online on how to thicken it.
400g mushrooms (I used white & chestnut) 1 large onion 1 litre boiling water 1 veg stock cube squirt of marmite 2 tbsp flour 100ml Alpro single cream
I chopped the onions and mushrooms very finely using a food processor but you could do it by hand, very tiny peices.
All put into the pressure cooker (except flour & cream), let the pressure up, turn down to medium heat for 20 minutes. When ready and steam released keep it on the heat and make the flour up in a little cold water and add to soup, let it bubble for a few minutes to thicken, when it thickens slightly add the cream.
So simple to make and tasted delicious. It's not too thick and a lovely flavour