Heat the broiler to high and place the peppers on a baking sheet. Broil for 5-6 minutes, turning the peppers often, until the skin is black.
Place the peppers in bowl, cover it tightly with plastic wrap and set aside for 10 minutes.
When the peppers are cool enough to handle, peel off the black skin and rinse under a tap to wash off the seeds and remaining skin, chop the flesh finely and set aside.
Place the chopped tomatoes with their juices in a pan and add the chopped garlic. Cook over a medium heat for 5 minutes, until thickened.
In a separate saucepan, heat a little oil and gently fry the onion and celery for 5 minute, or until softened. Once soft, add the rice, cook for a further 5 minutes, then stir in the white wine and allow the alcohol to evaporate off.
Add the broth, simmer over a medium heat for 20 minutes, stirring continuously until the rice has absorbed all the broth and is tender.
When the rice is almost ready, add chopped peeled peppers, tomatoes, parmesan, basil and butter. Stir vigorously, until the risotto is creamy. Season with salt and pepper, finish with a drizzle of olive oil and serve.