Thaw the frozen peas. In a large saucepan stir together white sauce mix and milk.* Following package directions, cook until thickened. Stir in cheese and pepper. Add macaroni, ham and peas and cook, stirring until heated through. Serve hot.
*If you want to make a white sauce from scratch, melt 3 tablespoons butter in a saucepan. Stir in 1/4 cup flour and cook until mixture bubbles. Stir in 2 cups milk and cook, stirring until thickened.