First make the mashed potatoes. Peel, dice then cook the potatoes in lightly salted water. When tender, drain and put them back in the pot. Add a large dollop of butter and mash into a textured purée. Add enough milk to be light but not too Thin. Season to taste.
Meanwhile, thinly slice the onion and chop the garlic. Cut the carrot and red pepper into small pieces.
Heat 2 Tbsp of oil in a large pan, then gently sauté the onion. When it's soft, add the garlic, red pepper and carrot. Sautee for 5 minutes (under cover), then add the mushrooms and oregano. Cook for another 5 minutes under cover, then add the gravy and tinned tomatoes.
Bring to the boil and gently simmer for 15 minutes, until the vegetables are tender.
Add your chosen chopped greens and cook for another 5 minutes, then fold in the shredded turkey meat and parsley.
Tur on the grill.
Spoon the stew into a large baking dish or individual dishes. Top with the mash, spreading it out evenly. It should completely cover the stew. Draw some lines on the top with a fork, then scatter the cheese all over it (if used).
Grill for 5-10 minutes until golden and crispy.
Serve warm.