In a large skillet over medium heat, heat the oil. Add the onion and cook for 5 minutes, stirring to caramelize but not over brown. Add butter and sugar and cook until onions have nicely caramelized, about 15 minutes. Remove from heat and cool.
Once cooled mix together the remaining ingredients except for the tortillas and vinegar; refrigerate for at least 4 hours.
After mixture has had time to meld, set aside 1/3 of the mixture for the dipping sauce and evenly spread the remaining mixture on the top of 11 tortillas. Stack the tortillas on top of one another, with the last tortilla on top having no mixture spread on it. Wrap tortilla stack in plastic wrap and let set up for 12 to 24 hours in refrigerator.
Heat a grill heat. Cut the stack into 16 wedges. Grill each wedge on each side until warmed and grill marks appear. Mix reserved mixture with balsamic vinegar for dipping sauce. Serve tortilla wedges with dipping sauce.
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