How to Make It
Cook sirloin in a large skillet over medium-high, stirring to crumble, until browned and cooked through, 6 to 8 minutes. Transfer to a bowl and stir in ketchup and mustard.
Combine mayonnaise, pickle juice, salt, and pepper in a small bowl. Set aside.
Top half of each tortilla with ¼ cup cheese. Top with ⅔ cup meat mixture, 6 pickle chips, and another ¼ cup cheese. Fold tortilla in half to cover filling.
Heat a medium skillet over medium. Spray outside of tortillas with cooking spray and, working in batches, add to skillet. Cook until cheese is melted and tortillas are golden brown, about 2 minutes per side. Transfer to a plate and cover to keep warm. Repeat with remaining tortillas.
Top each romaine half with some tomato, shallot, and a drizzle of mayonnaise dressing. Serve with quesadillas.