Preheat the oven to 375 degrees Fahrenheit (190 degrees Celsius). Grease a 2-quart baking dish with cooking spray and place the dish on a baking sheet.

Cook bacon in a large skillet over medium heat until crisp, about 10 minutes. Place bacon on paper towels to drain, then chop.

Boil salted water in a large pot, add baking potatoes, and cook until fork-tender (15–20 minutes). Drain and mash with evaporated milk, butter, 1/2 teaspoon salt, and 1/2 teaspoon pepper. Stir in 1/4 cup chopped bacon.

Using reserved bacon fat, cook ground beef, onion, and bell pepper until browned and cooked through (8–10 minutes).

Add corn, garlic, and smoked paprika to the skillet. Cook for 1 minute. Stir in barbecue sauce, Worcestershire sauce, Dijon mustard, 1 teaspoon salt, and 1/2 teaspoon pepper.

Spread ground beef mixture into the prepared baking dish.

Spread mashed potatoes evenly over the beef mixture. Top with cheese, remaining chopped bacon, and French fried onions.

Bake casserole in the oven until bubbly and cheese is melted, about 20–25 minutes.