Place vegetables in a Dutch oven. Add salt and enough water to cover. Cover and bring to boiling. Reduce heat to medium. Cook, covered, 15 to 20 minutes or until tender. Drain vegetables, reserving some of the cooking water. Using a potato masher, mash potatoes to desired consistency, adding reserved water as needed. Stir in cheese. Season to taste with salt and pepper. Cover and keep warm.
Meanwhile, preheat oven to 300°F. Rinse fish and pat dry with paper towels. Cut into 8 equal pieces. In a shallow dish, beat egg. In another shallow dish combine bread crumbs, dill, and 1/2 tsp. each salt and pepper. Dip fish pieces into eggs, then into bread crumb mixture. Set aside.
In a large skillet heat olive oil over medium-high heat. Add half the fish. Cook 2 to 3 minutes on each side or until fish is golden brown and flakes easily with a fork. Drain on paper towels. Keep warm in the preheated oven while frying remaining fish. Serve with cauliflower mash and lemon wedges. Sprinkle with additional fresh herbs, if desired.