Saute the mushrooms in olive oil for 3-4 minutes until golden, remove and set aside to cool
Add the red onions and leek, cook for 2-3 minutes, then add the, rosemary, sage and parsnips and cover with a lid cook for another 7-8 minutes, until the root veg is softened
Add back the mushrooms with cooked chestnuts and crumble in the walnuts stirring as you do
Add the spring greens for another 2 minutes and then pile into a large round baking dish
Gravy:
Meanwhile to make the gravy saute the shallot for 5 minutes in a pan with oil
Add the diced mushrooms, garlic, soy and Worcestershire sauce and cook for another 3-4 minutes
Add the corn flour, stock, milk and simmer for 5 minutes
Pour into a blender and process into a smooth gravy
Add the pie Ingredients to a large pie dish with a splash of gravy to loosen the mixture
Scrunch up some filo on the top and brush with oil