Roast the red peppers over an open flame or under the broiler until the skin is charred on all sides. Place them in a plastic bag and tie it shut. After about 20 minutes take the peppers out, cut them in half, remove the core and scrape away the skin and the seeds. Do not rinse them or try to peel them under running water or you’ll wash away the flavor. Cut the peppers into ¾-inch squares.
Fill a pot for the pasta with about 6quarts of water, cover, and place over high heat.
Put the olive oil and garlic in a 12-inch skillet and place over medium high heat. When the garlic begins to sizzle, add the shrimp, season with salt and pepper, and cook for 1-2 minutes, stirring often, until the shrimp have lost their raw color. Stir in the roasted peppers and add the cream and parsley. Cook until the cream has reduced by a third, then remove from the heat.
Add 2tablespoons salt to the boiling pasta water, add the spaghetti, and stir until all the strands are submerged. Cook until al dente. When the pasta is done, drain well, toss with the sauce, and serve at once.