Start potatoes boiling in a large pot of salted water.
Meanwhile, combine beef, onion, carrots, celery, salt, garlic, pepper, chili powder in a large pan and brown over medium-high heat. Once browned, cover and cook over medium heat (stirring occasionally), for 10-15 minutes until veg are cooked.
Drain potatoes and mash with milk, garlic and bouillon (I use the food processor for this so they're nice and smooth). Set aside.
Preheat oven to 350 degrees F. (*if baking right away)
To the beef, add peas, corn kidney beans, barbecue sauce and brown sugar (optional). Cook another 5 minutes until vegetables are warmed through.
To a 3qt casserole dish or a 9x13" pan, add the beef mixture. Top with mashed potatoes. Bake 20 minutes or until heated through. Top with cheese and broil 2-3 minutes, watching closely, until cheese is melted and lightly browned.
Video
Notes
*If storing in the fridge and baking later, you may have to bake the casserole 40 minutes to 1 hour until it is hot all the way through. Be sure to cover with an oven-safe lid or tin foil sprayed with non-stick spray. *Nutrition information is estimated and will vary depending on exact serving size, types and brands of products used.