In a 4- to 5-quart pan over high heat, bring broth, milk, and macaroni to a boil. Stir mixture often until the pasta is tender to bite, about 10 minutes.
Blend cornstarch and 3 tablespoons water until smooth. Stir into pan and continue stirring until mixture boils.
Add peas and Canadian bacon; mix well and remove from heat. Sprinkle cheese over pasta mixture and stir just until melted, 1 to 2 minutes.
Spoon into wide bowls or onto plates and sprinkle generously with pepper and nutmeg.