Combine coriander seeds, fennel seeds, and black peppercorns in a skillet.

Toast over medium-high heat until fragrant and slightly darker, about 2 minutes.

Transfer to a spice grinder and grind until finely ground.

Rub each lamb shank with 1 teaspoon of the spice blend, then sprinkle with salt and pepper.

Heat 2 tablespoons of olive oil in a large, wide pot over medium-high heat.

Add the lamb shanks and cook until browned on all sides, about 20 minutes. Transfer to a bowl.

Add the remaining 2 tablespoons of olive oil to the pot.

Add the onion, garlic, celery, carrots, and leek, and sauté over medium heat until the vegetables begin to soften, about 5 minutes.

Add the remaining spice blend and stir for 1 minute.

Pour in the ruby Port and simmer until the liquid is reduced to 2/3 cup, about 15 minutes.

Add the chicken broth and beef broth, then boil until the liquid is reduced to 3 1/2 cups, about 30 minutes.

Preheat the oven to 350°F (175°C).

Return the lamb shanks to the pot.

Add cloves, star anise, bay leaves, and crushed red pepper.

Cover the pot with foil, then with a lid.

Place the pot in the oven and braise the lamb until tender, about 2 hours.

Place 1 lamb shank on each of 4 plates.

Season the sauce to taste with salt and pepper.

Spoon the sauce and vegetables over the lamb shanks and serve.