Bake the green peppers in a hot oven, as soon as they soften wrap them up in a moistened cloth for 5 minutes, then remove their skin. Dice the green peppers. Heat the butter in a frying pan to fry the onions without allowing them to brown. Trim and discard the muddy bottom of the mushrooms, wash in acidulated water. Quarter them, rub with lemon juice to keep white, add to the onions. Cook quickly until their water evaporates. Add the green peppers, sprinkle with paprika, cook and stir for 3 to 4 minutes, then sprinkle with the cream into which you have dissolved the cornstarch. Allow to thicken, serve.