Rinse the pearl barley in a sieve under running water until the outer starch comes off. Place into a large saucepan and fill with cold tap water to cover the barley with a good 5 cm of water. Boil over high heat for 20-30 minutes until just tender. Taste a few grains to check they are bite-tender. Drain and place into a large mixing bowl. Set aside

Heat the oil in a large, deep frying pan and add the leek and capsicum and saute over medium heat until softened, about 3 minutes. Then add the carrot and garlic and cook for 1 minute more

Add the mushrooms and cook until browned and wilted, about 5 minutes. Add the tomatoes and a splash of water and cook for a further 3-4 minutes until tomatoes are softened, then mash roughly into the sauce. Season with salt and pepper

Pour the vegetables into the bowl with the barley and mix to combine. Heat the oven to 180°C

Make the white sauce. Melt the spread or butter in a small saucepan. Add the cornflour and quickly whisk to form a smooth paste. Gradually pour in the soymilk, constantly whisking, for 5 minutes or so until thickened enough to coat the back of a spoon. Stir in the mustard and white pepper

Pour the white sauce into the bowl with the barley and vegetables and mix to combine. Then pour into a 2L, ovenproof casserole dish and sprinkle with nutritional yeast or parmesan. Bake for 30 minutes until piping hot and browned