Rinse the green olives well, cover them with water, and place them in a small pot or saucepan. Add the vinegar and bring to a boil to remove excess salt. For best results, boil the olives three times, changing the water each time. Once done, drain the olives and set aside.

To prepare the kefta: In a large bowl, combine the ground lamb, onion, minced garlic, salt, black pepper, breadcrumbs, and chopped parsley. Mix well until everything is combined, then shape into small balls. Fry the meatballs in a little oil and butter until golden brown, then set aside.

To make the tagine sauce: In the same pot used to fry the meatballs, sauté the onion and garlic well. Add the mustard and black pepper, then add the mushrooms, green olives, and meatballs. Pour in a little hot water to cover.

Note: Use as little salt as possible since the olives and meatballs already contain some salt.

In a small cup, mix the flour with water until smooth, then pour it into the tagine sauce to thicken it slightly. Add the hot chili pepper and let everything simmer on low heat until the kefta tagine is cooked through.

Transfer the olive tagine to a serving dish and garnish with lemon slices and parsley on top. Enjoy!