Preheat the oven to 180°C/Fan 160°C/Gas 4. Lightly oil a 26 x 18cm baking dish. Place a medium frying pan on a medium heat. Add 2 tbsps of the oil, the onion, garlic and chopped sage. Sauté for 5–10 minutes until softened and starting to turn golden.
Tip into a mixing bowl and add the pumpkin purée, chestnuts, olives, chilli flakes, Parmesan and ricotta. Mix, season with salt and pepper and place to one side. For the sauce, put the milk, flour and butter in a medium saucepan on a medium heat. Whisk for 5–10 minutes until thickened. Stir in the ricotta and most of the Parmesan.
Spoon half the sauce into the baking dish. Pipe the filling into each pasta tube (use a freezer bag with a corner snipped off as a piping
bag), arrange in the dish and cover with the remaining sauce. Sprinkle over the remaining Parmesan, cover with foil and bake for 30 minutes.
Toss the breadcrumbs with 1 tbsp olive oil. Remove the foil, scatter over the breadcrumbs, then return to the oven for a final 10–15 minutes
until golden. Meanwhile, heat the remaining 1 tbsp oil in a frying pan, add the whole sage leaves, fry for a few seconds until crisp, then drain on a piece of kitchen paper. Remove the bake from the oven, allow to sit for 5 minutes, then serve topped with the fried sage leaves.