Step 1: Preheat your oven to 400°F (200°C). Lightly grease a 9x13 inch baking dish.
Step 2: In a large skillet, brown the ground beef over medium-high heat. If using, add diced onion and cook until softened. Drain any excess grease.
Step 3: Stir in the garlic powder, onion powder, salt, and black pepper into the browned ground beef. Cook for another minute.
Step 4: Reduce heat to low. Stir in the condensed cream of mushroom soup, milk, ketchup, and mustard until well combined and simmering. Remove from heat.
Step 5: Stir 1 cup of the shredded cheddar cheese into the beef mixture until melted and fully incorporated.
Step 6: Spread the beef and cheese mixture evenly into the prepared baking dish.
Step 7: Arrange the frozen French fries in a single, even layer over the beef mixture. Try to cover the entire surface for maximum crispiness.
Step 8: Sprinkle the remaining 1 cup of shredded cheddar cheese evenly over the French fries.
Step 9: Bake for 25-30 minutes, or until the fries are golden brown and crispy, and the cheese is melted and bubbly. For extra crispy fries, you can broil for the last 2-3 minutes, watching carefully to prevent burning.
Step 10: Let the casserole stand for 5 minutes before serving. Garnish with fresh parsley or chopped green onions, if desired.