Big Mac Casserole

Gather all ingredients. Preheat the oven to 400 degrees F (200 degrees F). 

Place hash brown patties in a single layer along the bottom of a 9x13 baking dish.  Bake in the preheated oven until golden and crisp on the bottom, about 25 minutes.

Meanwhile, grate or very finely mince 2 tablespoons of onion and set aside, along with any accumulated juices.  Cut the remaining onion into a
small dice and set aside.

While hash browns bake, combine grated onion with mayonnaise, 1/2 teaspoon salt, sweet pickle relish, white vinegar, sugar, mustard, paprika, and onion powder in a bowl and mix well.  Set aside.

Heat oil in a large skillet over medium-high heat. Add beef and cook, undisturbed for 3 minutes. Continue to cook, while crumbling the meat with the back of a spoon and stirring occasionally, until browned and mostly cooked through, about 5 minutes. Season with remaining salt, pepper, Worcestershire and remaining chopped onions and cook for 1 minute. 

Remove from the heat and stir in 2/3 cup of the sauce mixture and 1 1/3 cup cheese. 

Flip hashbrown patties over so the crispy side is on top. Pour meat mixture over hash browns and top with remaining shredded cheese.

Sprinkle with sesame seeds and bake until bubbly and cheese is melted, 10 to 12 minutes. Remove from oven and let stand for 5 minutes. 

Top with shredded lettuce and drizzle with remaining sauce. Top with chopped pickles and serve immediately.