Add the sauce ingredients to a bowl, and whisk to combine well. Set aside 3 Tbsp of the sauce mixture.
Preheat the oven to 400 degrees.
Place the ground beef and onions into a skillet over medium high heat.
Mix in the mustard, onion powder, garlic powder and salt and pepper to taste. Saute until the meat is browned completely and the onion is softened.
Remove the mixture from the heat, and drain any excess grease.
Stir the reserved 3 Tbsp of sauce into the meat mixture.
Line a baking sheet with parchment paper, and arrange the cheese in 8 circles, separate a bit from one another. You may need to do this in two batches depending on the size of your tray.
Bake the cheese until the circles have a lacelike appearance.
Remove the tray from the oven and let cool for 1 minute.
Place a layer of the meat mixture down the center of each cheese circle, and then top with the lettuce, tomato and pickles.
Carefully roll the cheese circles closed around the filling.
Allow the rollups to cool and crisp up.
Serve the rollups with the remaining sauce on the side.