Serves: 16 portions1) Heat the oil in a large skillet over medium heat. Add the onion and cook for 5 minutes, stirring to caramelise but not over brown. Add the butter and sugar and cook until the onions have nicely caramelised, about 15 minutes. Remove from the heat and cool.
2) Once cooled, mix together with the garlic, Parmesan, mayonnaise, coriander, salt and pepper and refrigerate for at least 4 hours.
3) After the mixture has had time to meld, set aside 1/3 for the dipping sauce and evenly spread the remaining mixture on top of 11 tortillas. Stack the tortillas on top of one another, with the last tortilla on top having no mixture spread on it.
4) Wrap the tortilla stack in cling film and refrigerate for 12 to 24 hours. When ready to serve, remove the stack and cut into 16 wedges.
5) Heat a barbecue and grill each wedge on each side until warmed and grill marks appear. Add the the balsamic vinegar to the reserved mixture to make a dipping sauce and serve with the tortilla wedges.