Heat the olive oil in a large non-stick frying pan over medium–high heat. Add the mushrooms and cook, stirring, for 3–4 minutes or until golden. Add the garlic and cook for 30 seconds or until fragrant. Add the beans and tomato and cook for 1 minute or until heated through. Season to taste with sea salt and freshly ground black pepper. Set aside.
Preheat a sandwich press. Spread a quarter of the mushroom mixture over half of a tortilla. Top with a quarter of the cheese, a quarter of the spinach leaves, and chilli sauce to taste. Fold the tortilla over to enclose the filling. Repeat with the remaining tortillas and fillings.
Spray the quesadillas on both sides with oil. Cook in batches in the sandwich press for 3 minutes or until the quesadillas are crisp and the cheese has melted. Serve with a dollop of yoghurt, garnished with coriander.