2 tbsp olive oil
2 onions, sliced
3 tsp brown sugar
1/3 cup (80ml) balsamic vinegar
20g unsalted butter
3 large garlic cloves, crushed
4 portobello or other large flat mushrooms, thinly sliced
3 thyme sprigs, leaves picked
8 flour tortillas or wholegrain wraps
200g vintage cheddar, grated
Handful rocket leaves, roughly chopped
1/2 cup (120g) sour cream
Juice of 1/2 lemon
Heat 1 tbs oil in a frying pan over low heat.
Add the onion and cook, stirring, for 10-12 minutes until soft. Add the sugar and balsamic vinegar, then cook, stirring, for a further 5 minutes or until the onion is caramelised. Remove the pan from the heat and set aside.
In a separate frying pan, heat the butter and the remaining 1 tbs oil over medium heat. Add the garlic, mushroom and thyme, then cook, stirring, for 3-4 minutes until soft. Remove the pan from the heat and set aside.
Heat a chargrill pan or large non-stick frypan over high heat. Add 1 tortilla and cook on one side for 30 seconds or until slightly toasted and charred. Remove from the pan, then repeat with the remaining tortillas.
Place 4 tortillas, toasted-side up, on a benchtop. Top each one with a quarter of the caramelised onion, mushroom mixture, grated cheese and rocket leaves, then sandwich with the remaining tortillas, toasted-side down.
Return the chargrill pan or frypan to high heat. Add 1 quesadilla and cook for 2-3 minutes until toasted on one side. Carefully flip, then cook for a further 1-2 minutes until the cheese is melted and the tortilla is toasted.
Keep warm while you repeat with the remaining 3 quesadillas.
Meanwhile, to make the lemon sour cream, combine the sour cream and lemon juice in a bowl.
Serve the warm quesadillas with a dollop of lemon sour cream.