Preheat oven to 400 degrees F. Cut 7 (2-foot) lengths of butcher's twine.

Cut open leg of lamb and arrange on work surface, inside facing up. Butterfly meat by cutting vertical slits in the thicker parts of the lamb without cutting all the way through. Flatten meat and trim off extra pieces, reserving them, until leg is a fairly even thickness; you should have about 1/2 pound extra meat. Place a sheet of plastic wrap over lamb and pound with a meat mallet until 1/4 inch thick. Remove plastic wrap and use a sharp knife to poke halfway into meat, taking care not to cut all the way through. Sprinkle 2 tablespoons of Creole seasoning over top of lamb and set aside.

Dice reserved 1/2 pound meat into 1/2-inch pieces. In a large skillet heat 2 tablespoons of the oil over high heat. Add diced lamb and 1 tablespoon of the Creole seasoning and brown 3 minutes. Add onions, garlic and 4 turns of black pepper; saute, stirring constantly, 1 minute. Remove from heat and add spinach and mint. Transfer to a bowl to cool.

Spread half of stuffing mixture lengthwise along one side of lamb, dot with goat cheese and top with remaining stuffing. Roll up lamb over stuffing, tucking in ends. Space 6 pieces of twine under lamb roll and tie them firmly, starting at outside and working in. Tie roll lengthwise with remaining piece of twine. Sprinkle outside of roll with remaining tablespoon Creole seasoning.

In a large skillet heat remaining 1 tablespoon oil over high heat. Add lamb roll and sear on all four sides, 6 minutes in all. Transfer lamb to a roasting pan and roast until brown and tender, 30 minutes for rare, 35 minutes for medium rare, basting occasionally. Remove from oven and let sit, covered loosely with foil, 10 minutes. To serve, discard strings, slice in 16 pieces and serve 2 slices per serving.