Smash the chickpeas in a small bowl using the back of a fork, so that some are partially smashed and some are left whole. Add the tomatoes, garlic, coriander, mint, olive oil and lemon juice, then scatter over the pine nuts0.
Preheat the grill to high. Lay the prepared sardines skin side-up in a single layer on a lined baking tray. Mix together the parsley, coriander, lemon zest and juice, sumac, garlic and Greek yogurt in a bowl. Spoon evenly over the sardines, making sure they are all covered.
Grill for 5 minutes, or until the sardines are completely cooked through and the skin is blistered. Serve immediately with the salsa.