In a large skillet over medium-high heat, add the ground beef and onion seasoning and cook until browned. Drain any grease from skillet.
Add in ketchup and mustard, salt and pepper and mix well.
Layer beef mixture into a casserole dish that has been sprayed with cooking spray in an even layer.
Add a single layer of pickle slice (chips).
In the same skillet you cooked the beef in, add butter and melt completely over medium heat. Add flour and continue to stir until the mixture is golden brown (approx 5 minutes).
Add milk to the rue mixture and stir until fully incorporated (3 minutes)
Slowly add in 1.5 cups of cheese and stir until the sauce has thickened and if you run a spoon down the center of your pan, the line remains after 5 seconds.
Transfer the cheese sauce to the casserole dish, evenly layering on top of the beef and pickle layers.
Finish the casserole by layering tater tots in a single layer but placed close to one another. I used approx 50 tots.
Bake at 350 for 35 minutes. Remove add the remaining half cup of shredded cheese and return to oven for an additional 5 minutes. Garnish with chopped parsley if desired.
Notes
Half a minced fresh onion may be substituted for dried onion spice. Saute with the beef while it browns. BBQ sauce can replace the ketchup and mustard. Bacon bits or chopped bacon slices can be layered on top of the meat and pickles if desired.Not a fan of pickles? Replace with 2 tbsps relish for a more subtle flavor. Add relish when adding ketchup and mustard.