Lay out tortillas on a work surface. Spread cream cheese evenly over all 4 tortillas. Spoon black beans over 2 tortillas then crumble bacon over beans. Sprinkle bacon with green onions and coriander and divided grated cheeses evenly between the 2. Add hot sauce if you wish, sandwich tortillas together and press gently.
Heat a large sauté pan over medium heat. Add 1 tablespoon of oil and gently place in quesadilla. Cook until tortilla is crisp and golden, about 4 minutes, then gently flip and cook until crisp, another 3 to 4 minutes. Remove and let rest for 3 minutes before slicing. Repeat with remaining quesadilla.
Slice each quesadilla into 6 and serve with salsa and sour cream.