Put about 3 cups stale Italian bread on a baking sheet and put in hot oven. Bake for 10 minutes, cool and add to the bowl of a food processor fitted with a bottom blade. Pulse into crumbs.
Bring a large pot of water to a boil over medium heat. Salt the water and add the pasta. Cook until al dente. Remove 1 cup of the cooking water and reserve. Drain the pasta and set aside.
In a large saute pan, add 4 tablespoons of the olive oil and the bread crumbs and cook over medium-high heat until golden and well coated. Remove from the pan to a plate.
Add the remaining 4 tablespoons of the oil to the pan and when hot, add the anchovies and the minced red bell peppers and cook, rapidly, stirring them around with a wooden spoon, for about 2 minutes. Add the onions and cook for 6 to 8 minutes, stirring frequently. Add the garlic and chili flakes, cook for an additional 3 to 4 minutes. Add 1/2 to 1 cup of the bread crumbs and half of the cheese. Stir in the pasta, toss to combine, adding the cooking liquid as needed.
Transfer to a serving platter and garnish with remaining cheese, bread crumbs and parsley. Serve immediately.