Preheat an oven to 210C. Prick the potatoes a few times with a fork rub with 1 tbsp of olive oil and some salt. Place on a baking tray and roast for 45-50 minutes, until soft.
Meanwhile, combine the yoghurt, herbs, lemon and a little seasoning in a small bowl and set aside.
When the potatoes are close, place a large pan over medium high heat and add the remaining olive oil the onion, garlic, mushrooms, spices and a little salt. Cook, stirring often to begin cooking the mushrooms, approx. 2 minutes then add the butter and continue to cook for another minute before adding the spinach to just wilt through.
Combine the onions, pickles, herbs and sumac in a bowl.
Place the potatoes onto serving plates, split open the potatoes with a knife and gently break with flesh with a fork.
Spoon over the mushrooms some yoghurt and scatter over the pickle salad. Serve with lemon wedges.
