Saute mushrooms in 1oz butter, squeeze lemon and salt and pepper. Set aside.
Put parsnip, sweet potato and onion in a roasting tray with 1 tbsp olive oil and 1oz butter. Roast until cooked. Put in bowl, add half chickpeas and crush with a fork until forms a rustic mash. Add rest of chickpeas, coriander, thyme and the zest and juice of an orange. Fold together and season to taste.
Make 3-4 pancakes as thin as you can. Roll out pastry to a thin 14inch rectangle and add pancakes, layered and overlapping. Add mushrooms to the centre of the pancakes and then add rest of the filling. Seal each end and roll over pancakes. Egg wash one side of inside puff pastry and roll up like a sausage roll. Crimp the edges to seal and score the top in a pretty pattern of your choosing. Brush with beaten egg and cook in the oven at 180°c until golden brown (approx 40-50 mins).
Put all ingredients in pan and boil gently for 20 minutes. Serve in a gravy boat to accompany the above.