Preheat oven to 325°. In a large frying pan over medium-high heat, warm 1 tablespoon of the butter or oil per serving. Working in batches, add the meat and fry, turning, until browned on all sides, about 10 minutes. Using a slotted spoon, transfer to a baking dish or stew pot. Add the onions to the fat remaining in the frying pan and sauté over medium heat until tender and translucent, 8 to 10 minutes. Add the garlic, cumin, coriander, tomatoes, tomato paste and 1 cup stock and mint, if using. Stir well. Pour over meat and season with salt and pepper. Cover and bake until all liquid is absorbed, about 1 1/2 hours. Taste and adjust the seasonings. Meanwhile, prepare the okra. Okra must be cooked so that its slimy texture is eliminated. Trim the conical tops with a sharp knife, then soak the okra for 30 minutes, allowing 1/2 cup vinegar per pound. Drain, rinse and dry the okra. In a sauté pan over medium heat, warm the remaining 1/2 tablespoon (per serving) of butter or oil. Add the okra and sauté for 3 minutes, stirring gently. Remove the stew from the oven and arrange the okra on top in a spoke pattern. Sprinkle the lemon juice evenly over the surface. Re-cover the dish and return it to the oven. Bake for 35 minutes longer. Add stock or water if the mixture seems too dry.