For quesadilla, place four of the tortillas onto a board and cover each with the grated cheese.
Divide the chicken, red onion, jalapeno chillies and coriander equally over the cheese-covered tortillas.
Spread the sour cream onto one side of each of the remaining four tortillas and place sour cream-side down onto the filled tortillas.
Heat a frying pan and add the oil. Carefully place a quesadilla into the frying pan and cook over a medium heat for 3-4 minutes, until crisp and golden and the cheese filling is melting. Carefully turn the quesadilla over and cook on the other side for a further two minutes, or until crisp and golden. Remove from the pan and set aside to keep warm. Repeat with the remaining quesadillas.
Cut the quesadillas into quarters and serve fresh and hot.
For the salsa, place all of the salsa ingredients into a food processor and pulse to combine. Season, to taste, with salt and freshly ground black pepper.
To serve, arrange the quesadillas serving plate and place a bowl of salsa into the middle.