Preheat the oven to 220ºC.
Put the red pepper chunks and cherry tomatoes onto two halves of a baking tray, with the tomatoes cut-side up. Spray with low-calorie cooking spray, then season to taste with salt and pepper.
Roast for about 10 minutes, or until the red pepper chunks are slightly charred around the edges. Then remove the red pepper chunks from the oven, and set aside. Continue to roast the tomatoes for a further 10 minutes — or until they're wrinkling a little and starting to brown around the edges — then remove from the oven and set aside. Lower the oven temperature to 180 ºC fan.
Meanwhile, spray an oven and hob-safe casserole dish — approx. 24cm diameter — with low-calorie cooking spray. If your casserole dish isn't hob-safe, you can use a large frying pan instead for this step. Place over a medium heat, and add the onion, garlic, and chopped roasted red peppers from the jar. Cook gently for 10 minutes, until the onions are soft, stirring occasionally.
Add the passata, balsamic vinegar, Worcestershire sauce, vegetable stock, paprika, and dried basil. Stir to combine, then transfer to a food processor or use a stick blender to blitz until smooth (you will probably need to do this in batches, depending on the capacity of your food processor).
Return the smooth mixture to the casserole dish and add the orzo, charred red pepper chunks, and the mushrooms. Stir well, cover tightly with a lid or kitchen foil, then bake in the oven for 10 minutes.
Remove from the oven and stir in the green beans. Cover and return to the oven for a further 20 minutes, stirring halfway through, until the orzo and beans are tender.
Remove from the oven and stir in the roasted tomatoes, crumbled feta, and basil leaves. Serve hot.