Preheat the oven to 200C/400F/Gas 6 (180C fan)
Cut the partridge into 2.5cm pieces. Season the flour with salt and pepper and toss the meat in the flour until completely coated. Save any excess flour then heat the oil in a large frying pan and brown the meat on all sides, remove from the pan and pour into a pie dish.
Peel and chop the onion and garlic and dice then cook in the pan with a little more oil if required until softened. Peel and dice the celeriac and carrots into 2cm pieces and add to the carrots and cook over a medium heat for 5 minutes then add the reserved flour and stir for 2 minutes.
Pour in the stock, wine and chopped parsley and bring to a boil. Season then reduce the heat and leave to cook for 10 minutes then pour over the meat in the pie dish.
Roll out the pastry to the size of the pie dish and place on top of the meat and vegetables. Score with a sharp knife and brush with beaten egg. Cook in the oven for 30 minutes until the pastry is golden.
Remove from the oven and cut into 4 pieces and serve with creamed potatoes and steamed greens.