Bring the stock to boil and add the pearl barley. Cook for 10 minutes until soft. Drain.
Heat a sauté pan with the rapeseed oil. Gently fry the mushrooms for a couple of minutes. Mix in the pearl barley and Ras el hanout.
Make the sauce by blitzing together the plum tomatoes, purée, ground coriander, garlic, salt and pepper.
Stuff each pepper with the barley mix. Put in a small oven dish and pour over the sauce. Cook in the oven for 25 minutes, until soft but still holding their shape. Serve immediately with a good sprinkle of fresh chopped parsley.