Cook pasta according to package instructions until al dente. Drain and set aside.
- In a large skillet over medium heat, cook ground beef, onion, and garlic until beef is browned and onions are tender. Drain excess fat. Season with salt and pepper.
- In a small bowl, mix all Big Mac sauce ingredients until smooth.
- In a large bowl, combine cooked pasta, beef mixture, and half of the Big Mac sauce.
- Transfer mixture to a greased baking dish. Spread remaining sauce over the top.
- Sprinkle shredded cheddar cheese and chopped pickles evenly over the casserole.
- Bake at 350°F (175°C) for 20-25 minutes, until cheese is melted and bubbly.
- Remove from oven and top with shredded lettuce before serving.