Thinly slice the onion and garlic, then chop the mushrooms and red pepper.
Heat the oil in a frying pan and gently sauté the onion for 5 minutes until soft, then add the garlic, red pepper and mushroom pieces.
Add the oregano and chilli flakes, if used. Stir for a minute.
Add the lemon juice and a drop of water. Season with salt and pepper. Put a lid on and cook, over low heat, for 5 minutes. Add the broad beans and cook for another 5-8 minutes, until the beans are tender.
Stir in the lemon zest, then serve with chopped parsley leaves scattered on top.