Heat butter and oil in a large sauté pan over medium heat; add prosciutto and sauté for about 4 minutes. Add onion and reduce to medium-low heat, cook 4 additional minutes or until onions are opaque and pale yellow. Stir in tomatoes and red pepper flakes; gently simmer uncovered for 20 minutes. Remove from heat and set aside.

Steam garden peas for 3 to 4 minutes; remove from steamer and set aside.

Meanwhile, cook penne pasta according to package directions; drain and transfer back to pot in which they were cooked. Add garden peas and half prosciutto mixture; toss to coat evenly. Season to taste with salt and pepper.

To serve, transfer pasta to a large serving plate; top with remaining prosciutto mixture and garnish with Parmesan cheese and parsley.