Heat the oil in a large pan, then fry the celery for 6 mins until starting to turn golden. Add the carrots and thyme, and cook for 4 mins more.
Stir in the mince, breaking it up with the spoon. When it has turned brown, add the gluten free flour. Cook for 1-2 mins, then gradually add the low FODMAP stock and red wine. Cover and simmer for 35-40 mins.
Meanwhile, boil all the potatoes for 15-20 mins until tender, then drain and mash with the pumpkin puree, nutmeg and black pepper.
Spoon the meat mixture into a 2-litre ovenproof dish, spread or pipe the potato mixture on top, then grill until the topping starts to brown. (If making ahead, reheat in the oven at 180C/160C fan/gas 4 for 45 mins.) Serve with vegetables.
