Pre-heat your oven to 180C Fan/200C/375F/Gas Mark 5
Peel the butternut squash and chop into chunks, toss them in 1 tbsp of the oil and place into a roasting tray or onto a baking tray. Roast them for 15 minutes
Meanwhile, chop up the leeks and toss them in 1 tbsp oil. Remove the tray with the butternut squash from the oven and add the leeks to the tray. Roast for 20 more minutes
Once done, put the roasted leek and squash in a bowl and leave them to cool down completely
Pre-heat the oven to 160C Fan/180C/350F/Gas Mark 4
Roll out 350g of the pastry on some cling film or a floured surface
Line the tin with the pastry and trim the edges, leaving a little overhang. Prick with a fork all over
Line the pastry with baking paper and add baking beans or dried rice, bake for 15 minutes, then remove the paper and baking beans/rice, and bake for a further 10 minutes
To the cooled squash and leek add the ricotta, parmesan, dried sage and nutmeg. Fill the pastry base with the filling
Roll out the rest of the pastry and cut out strips. Make a lattice top by weaving them together. Brush all around the edge of the pie with beaten egg, then put the lattice on top and trim the edges. Press the lattice down to the edge of the pie, then brush more beaten egg all over the pastry
Bake the pie for 35 minutes until it is golden brown all over and bubbling