1 To make the pickle, whisk the vinegar with the sugar, salt, chilli flakes, mustard seeds and dill. Add the red onion and cucumber and coat in the vinegar. Allow to sit for at least 15 mins. Heat the grill to a high heat. Mix the yoghurt with the garlic and mustard.
2 Heat the grill to a high heat. Mix the yoghurt with the garlic and mustard.
3 Drizzle a little olive oil on one side of each flatbread, scatter with a pinch of sea salt and grill with that side up for one minute. Remove from the grill, turn over and spread with the mustard sauce.
4 Top with some torn up sliced ham, the Leerdammer, red onion and capers, dot over a little more mustard sauce, then grill for a couple of mins, until the cheese is melted. Serve with the drained cucumber pickle on top and extra mustard sauce.