Prepare pasta and peas according to package directions.
Cook prosciutto, pancetta, or bacon in a lightly greased skillet until crisp.
Meanwhile, melt butter in a large saucepan over medium heat. Gradually whisk in flour until smooth; cook, whisking constantly, 1 minute. Gradually whisk in milk and next 3 ingredients; cook, whisking constantly, 8 to 10 minutes or until thickened. Remove from heat.
Gradually stir in Cheddar cheese, stirring until cheese is melted and sauce is smooth. Stir in hot cooked pasta, peas, and prosciutto. Serve immediately.