Step 1Trim the fat from all of the legs and render it. Reserve 2 tablespoons for preparing this dish; save the rest for some other purpose. Score the fatty skin without piercing the flesh. In a large, deep skillet over low heat, warm the rendered fat. Add the duck legs, skin side down, and cook, turning once, until browned, about 5 minutes per side. Pour off all the fat in the skillet. Season the legs with salt and pepper.
Step 2Add the onion, raise the heat to moderate, and cook, stirring, for 5 minutes, until softened and golden. Add the tomato, thyme and bay leaf and cook for 1 minute. Add the stock and wine and bring to a boil. Reduce the heat and simmer for 10 minutes. Cover and simmer until the legs are tender, about 1 1/2 hours, turning the duck legs from time to time [adding one-half cup water toward the end of cooking time if needed]. Note: Muscovy ducks will take an additional 30 to 60 minutes to cook. (The recipe can be prepared to this point up to 1 day in advance. If made ahead, reheat gently before proceeding.)
Step 3When ready to serve, add the sauteed eggplant and the olives to the duck legs with their sauce and gently stir to combine. Correct the seasoning and serve at once garnished with garlic toasts.