Start by sautéing onions, garlic, ginger, and meat on the stove. Transfer the mixture to a slow cooker along with all the ingredients, except for mushrooms and potatoes. Cook on low for 2-3 hours. Then add the potatoes, roasted mushrooms, olives, preserved lemon, lemon juice, and continue cooking for another 2-3 hours until the meat is tender. Before serving, garnish with cilantro.