Whisk all the dressing ingredients together. If it's too thick to drizzle, you can thin it out with just a bit of water. Set aside while you cook the beef
Beef
Warm a large skillet over medium-high heat. Once hot, spray with nonstick spray and add the ground beef. Cook, undisturbed for 1 minute, so it can develop a nice brown color. Then sauté, breaking it up into tiny crumbles, until cooked through and no pink remains. Drain off the fat, then season with the salt, pepper, and garlic powder. Transfer beef to a shallow bowl to cool slightly.
Assembly
In rows, divide the lettuce between 4 salad bowls. Top with about 1/3 cup beef, the cheddar cheese, diced onion, and pickles. Drizzle about 3 tablespoons of the Big Mac sauce over each salad and toss to coat. Garnish with a little bit of toasted sesame seeds.