Set a large skillet over medium-high heat. Add the bacon and cook, stirring often, until golden brown and crispy, about 5 to 8 minutes. Use a slotted spoon to drain the bacon and transfer to a plate lined with paper towels, set aside. Discard all but 1 tablespoon of bacon fat and return to the heat. Add the beef and cook, breaking up with a wooden spoon, until browned and no longer pink. Season with salt, pepper, garlic, onion, and cayenne. Stir in the cooked bacon, mustard and ketchup. Reduce heat to low to keep warm.

To make the cheese sauce, set a medium saucepan over moderate heat along with the butter. Once melted, whisk in the flour and cook for about 30 seconds. Slowly whisk in the milk and cook until thickened. Season with salt, pepper, mustard powder, garlic, onion and cayenne. Reduce heat to low and stir in the cheeses until smooth and melted through.

To make the special sauce, in a medium bowl, stir together the mayo, mustard, ketchup, relish, vinegar, cayenne, and a pinch of salt and pepper until well combined. Give it a taste and adjust seasoning accordingly. This can be made up to 3 days in advance and stored in the fridge until ready to use. It’s best if made earlier!

To assemble the nachos, pile the tortilla chips onto a large platter. Spoon the cheese sauce over the chips and top with the bacon and beef mixture. Top with lettuce, tomato, pickles, onion, and sesame seeds. Finally, drizzle with the special sauce and serve immediately. Enjoy!