Preheat your oven to 325°F (163°C).

In a small bowl, combine the toasted fennel seeds, crushed pink peppercorns, salt, and pepper. Rub this spice mixture all over the lamb shoulder, ensuring it's well coated.

In a large oven-safe skillet, heat the olive oil over medium-high heat. Once hot, add the lamb shoulder and sear on all sides until browned, about 4-5 minutes per side. Remove from heat.

In a separate bowl, whisk together the tamarind paste, honey, soy sauce, Dijon mustard, garlic powder, and onion powder until smooth. Brush this glaze generously over the seared lamb.

Cover the skillet with aluminum foil and place it in the preheated oven. Roast the lamb for about 3-4 hours, or until it is fork-tender. Remove the foil for the last 30 minutes of cooking to allow the lamb to caramelize.

While the lamb is roasting, place the eggplant rounds on a baking sheet. Drizzle with olive oil, and season with salt and pepper. Roast in the oven for the last 30 minutes of the lamb’s cooking time, until golden and tender.

In a small saucepan, combine the tahini, lemon juice, and vegetable broth. Whisk together over low heat until smooth and warmed through. Adjust seasoning with salt and pepper as needed.

Once the lamb is done, remove it from the oven and let it rest for 15 minutes before slicing. Serve the sliced lamb over the roasted eggplant, drizzled with the tahini gravy. Garnish with fresh herbs, if desired.