Wash the spinach thoroughly, remove and discard the stems, roughly chop, and set aside.
Heat the oil in a heavy pot over medium heat. Add the onions and saute until softened, stirring frequently. Add the lamb and saute, turning to brown on all sides. Add the Mixed Spices, salt, pepper, and water, and bring to a boil. Reduce the heat to low, cover, and simmer 1 hour or until the meat is tender and most of the water has been absorbed. If it has not, uncover and boil until the liquid is reduced. Stir in the spinach, cover, and simmer an additional 10 minutes. Stir in the lemon juice, and adjust the spices to taste. Turn off the heat.
In a small skillet, melt the butter. Add the pine nuts and saute until golden brown, stirring frequently. Stir in the red pepper and remove from the heat.
To serve, spread pieces of the toasted pita in the bottom of a serving dish. Spoon the lamb and spinach stew over them. Cover with the yogurt sauce and garnish with the sauteed pine nuts. Dribble the red pepper butter remaining in the skillet over the top.