Drain the beans, reserving 2 tbsp of the can water. Tip into a bowl with the reserved water, chipotle sauce, coriander and half the cheese. Mash everything well with a fork or potato masher.
Lay out 4 tortillas, then spread each with of the cheesy beans. Top with the remaining cheese, then top with another tortilla and use your hands to press them together.
Heat a griddle on a medium-high heat. Microwave each quesadilla for 45 secs to start the cheese melting, then griddle for 1-2 mins on each side, until the quesadillas are golden and charred. Repeat with the rest, keeping warm in a low oven.
