Preheat your oven to 350°F.
In large, nonstick skillet, cook your ground beef, onions and bell pepper over medium-high heat for 6-8 minutes. Heat until beef is no longer pink and then drain.
If you want mushrooms add them now. Also add your Montreal seasoning. Cook for 3-5 minutes, stirring occasionally.
Reduce heat to medium-low. Stir in the Velveeta cheese and beef broth. Cook 1-2 minutes or until cheese is melted, stirring frequently.
Pour into an ungreased 2-quart baking dish.
Cook your potatoes as instructed on the pouch. Spoon potatoes on top of your beef mixture.
Bake 25-30 minutes, until bubbly around the edges.
Remove from oven and over the top with Cheddar cheese. Return to oven and bake an additional 2-5 minutes, until the cheese is melted.