Preheat the oven to 400°F (200°C). Prick the eggplant with a fork and place it on a baking sheet. Roast for about 30-40 minutes, or until the skin is charred and the flesh is tender.

Remove the eggplant from the oven and let it cool. Once cool, scoop out the flesh and place it in a bowl.

Add yogurt, tahini, minced garlic, lemon juice, and salt to the bowl with the eggplant. Mix until smooth and creamy. Adjust seasoning if necessary. Drizzle with olive oil and garnish with fresh parsley. Set aside.

In a large bowl, combine the flaked fish, mashed potatoes, breadcrumbs, chopped parsley, onion, garlic, lemon zest, and beaten egg. Season with salt and pepper to taste. Mix until well combined. If the mixture seems too wet, add a bit more breadcrumbs.

Shape the mixture into patties, about 2-3 inches in diameter.

Heat oil in a large skillet over medium heat. Once hot, add the fishcakes in batches, making sure not to overcrowd the pan. Fry for about 4-5 minutes on each side, or until golden brown and cooked through. Remove from the skillet and drain on paper towels.

Plate the fishcakes and serve with a generous dollop of eggplant yogurt sauce on the side. Garnish with additional parsley if desired.