Preheat the oven to 375°F (190°C).
Brown the ground beef with diced onion and season lightly; drain well to avoid grease.
In a bowl, whisk together the mayonnaise, eggs, mustard, and Worcestershire sauce until smooth.
Layer bread or buns in the bottom of the dish if using, then spread the cooked beef on top.
Pour the sauce mixture evenly over the beef, then sprinkle with cheddar cheese.
Top with one even layer of frozen French fries.
Bake for 45 minutes, or until hot, bubbly, and fries are crispy and golden.
Rest for a few minutes before slicing and serving.
