Heat oven to 350°F. Line a rimmed baking sheet with foil; set aside.
For Mornay sauce, combine broth and butter over medium heat in medium-size saucepan. Whisk in Alfredo sauce mix. Bring to a boil over medium-high heat, stirring constantly. Reduce heat to medium; simmer for 2 minutes. Add 1-1/4 cups of the Swiss cheese, stirring for about 8 minutes or until melted. Remove from heat and set aside.
Place split English muffins on prepared baking sheet. Divide turkey among muffin bottoms. Stack with Canadian bacon and tomato slices. Top with about 1 cup of the Mornay sauce; reserve remaining sauce for another use. Sprinkle with remaining 1/2 cup Swiss cheese.
Bake tops and bottoms at 350°F for 30 minutes until stacked bottoms are heated through, cheese is bubbly and tops are toasted. Place muffin tops on sandwiches and serve.