Make guacamole by mashing the avocado together with the lime juice and coriander. Season with salt and pepper.
Spread two flour tortillas with the pesto and top with half the ham, cheese and spinach. Top each with another tortilla.
Place each quesadilla carefully into a non-stick fry pan and cook for 2-3 minutes each side, until golden and crispy. Alternately, cook in a sandwich maker for 3 minutes. Cut into quarters and serve with a dollop of guacamole.