Preheat oven to 325°. In a large bowl, whisk eggs, milk, salt and pepper until blended. Pour into a 13×9-in. baking pan coated with cooking spray. Bake for 15-18 minutes or until set. Cool on a wire rack.
Meanwhile, toast English muffins (or bake at at 325° for 12-15 minutes or until lightly browned). Butter the muffin bottoms, 1 tsp. on each.
Cut eggs into 12 portions. Layer muffin bottoms with Canadian bacon, an egg portion, and a cheese slice (tearing cheese to fit). Replace muffin tops. Wrap sandwiches in foil; freeze in a freezer container or bag.
To use frozen sandwiches: Remove foil. Wrap sandwich in a paper towel and microwave at 50% power until thawed, 1-2 minutes. Turn sandwich over; microwave at 100% power until hot and a thermometer reads at least 160°, 30-60 seconds. Let stand 2 minutes before serving.