Combine the red onion and radish in a bowl with juice from half of the lemon and pinches of salt and pepper. Stir well, then leave to one side to quickly pickle.
Add a tablespoon of coconut oil to a pan on a medium heat. Next add the ginger, cumin seeds and turmeric, then stir and cook for 2-3 minutes to lightly toast the spices.
Meanwhile, add the chickpeas to a mixing bowl and mash them with a fork until most of the chickpeas have broken down. Next add the yoghurt to the bowl, followed by all the oil, spices and ginger from the pan, as well as the raisins, juice from the remaining half of lemon and pinches of salt and pepper. Give the mixture a really good stir, then set aside.
Toast the bread, then spoon some yoghurt on one slice. Top with lettuce leaves, half of the chickpea mixture and slices of tomato. Spoon some more yoghurt on another slice of bread and top that slice with half of the pickled red onion and radish, then place it on top to make the sandwich. Repeat for the remaining sandwich and enjoy!