To reheat leftover quesadillas warm them in a dry frying pan.
In a bowl, combine the beans, cheese, chives, and cumin.
Divide the bean/cheese mixture evenly among five of the tortillas, then top with the remaining tortillas.
Heat the canola oil in a large nonstick skillet over medium heat. Cooking in batches so there is no overlap in the pan, add the quesadillas and cook for 2 to 3 minute per side, until cheese is melted and tortillas are golden brown.
Cut each quesadilla into wedges and serve with salsa and sour cream if desired.