Preheat and prep
Preheat your oven to 375 °F (190 °C). Lightly grease a 9×13‑inch (or similar) baking dish.

Cook the beef and aromatics
In a large skillet over medium‑high heat, cook the ground beef with the diced yellow onion and minced garlic until the beef is browned and onions are softened, about 6–8 minutes. Drain any excess fat.

Season and add soups
Stir in the cream of mushroom soup and cheddar cheese soup, along with garlic powder, onion powder, salt, and black pepper. Mix until well combined and slightly thickened, about 2–3 minutes.

Layer fries and beef mixture
Spread half the bag of shoestring French fries evenly across the bottom of the greased baking dish. Spoon the beef‑soup mixture over the fries, spreading evenly. Sprinkle half of the shredded cheddar cheese on top. Layer the remaining fries, followed by the rest of the cheddar cheese.

Bake
Bake uncovered in the preheated oven for 25–30 minutes, or until the fries are golden brown and edges are bubbly.

Make the burger sauce
While the casserole bakes, whisk together the mayonnaise, ketchup, mustard, pickle juice, dehydrated onions, and black pepper in a small bowl until smooth and tangy.

Finish and serve
Remove the casserole from the oven and let it rest for 5 minutes. Drizzle the burger sauce across the top—or serve it on the side for dipping. Slice into squares and serve warm.