The trick with quesadillas is to keep the filling really simple, then go a bit mad with your sides.
For the salsa, add a little oil, the mustard seeds and chilli to a small pan over a medium–high heat. When it’s fragrant, add the pineapple and juice, and a big pinch of pepper. Cook for 5 minutes, till thick and sticky. Squeeze in the lime, then put in a serving bowl.
For the guacamole, squeeze the avocado flesh into a bowl. Add the coriander, onion, chilli and lime juice. Season; add the tomatoes, picking out any larger bits of skin. Mix well, with a potato masher or hand blender, and then set aside.
Stir the lime juice and a pinch of salt and pepper into the cottage cheese. To assemble, mix the peppers, chilli and coriander with the Cheddar. Scatter across two tortillas, then top with the remaining tortillas. Cook in a non-stick pan for 2–3 minutes each side, or till the tortillas are golden and the cheese melts. Cut into quarters and serve with those delicious sides.