Bring large pot lightly salted water to boiling for pasta. Add pasta; cook 12 minutes or until firm but tender. Add peas for last 3 minutes of cooking. Reserve 1/2 cup of pasta cooking water; drain pasta.
Meanwhile, shake together flour and milk in jar with tight-fitting lid until blended. Heat butter in saucepan over medium heat. Add garlic; sauté 1 minute.
Whisk in milk mixture. Simmer 3 minutes. Whisk in cream cheese, 2 tablespoons Parmesan, salt and pepper. Simmer, whisking, 2 minutes. Remove from heat.
Toss together pasta, sauce and ham in large bowl. Add 1/4 to 1/2 cup of reserved pasta water, tossing to make creamy sauce. Top with remaining Parmesan. Serve hot.