How to Make It
Preheat the oven to 350°. Peel the butternut squash and cut into 1/4-inch squares, discarding the seeds and fibrous parts of the squash, but not the skin or scraps. Reserve the peeled skin and remaining scraps for the stock. Place the 1/4-inch pieces on a baking tray and season with, salt, pepper, sage leaves, and drizzle with olive oil over the top. Cover with foil and bake for 20 minutes until cooked through. Remove from the oven and set aside.
Meanwhile, make a quick squash stock, combine the squash peelings and scraps, roughly chopped onion, celery, peppercorns, and bay leaves in a 3 quart saucepot with 6 cups of water. Slowly bring the stock to a boil. Once it comes up to a boil, turn off the heat. Let it sit warm on the stove and after 20 minutes, strain out the solids and pour it back into the saucepot. Cover and keep hot over low heat.
In a large saucepan, heat the olive oil and 1 1/2 tablespoons of butter. Add the diced onion, and cook over low-medium heat, stirring occasionally until translucent and glossy, about 6 minutes. Add the rice to the onions and stir until rice is evenly coated, about 2 minutes. Add the wine and simmer until almost evaporated. Add enough of the hot butternut stock just to cover the rice; cook while stirring, until the stock is almost absorbed. Repeat with about 5 additions of stock until the rice is al dente and bound in a creamy consistency, about 25 minutes. There should be about a 1/2 cup of stock remaining, keep it hot and reserve.
When the rice is cooked, remove from the heat and carefully fold in a 1/2 cup of Parmesan, the remaining 2 1/2 tablespoons of butter, and roasted squash. Add the reserved stock to loosen and let the whole pan rest for a few minutes.
Meanwhile, in a heavy bottomed frying pan over medium to high heat, heat 1 tablespoon of olive oil until it begins to shimmer in the pan. Make sure the prawns are dry, and season with kosher salt. Once the oil is hot, drop them into the pan. Cook for 1-2 minutes on each side until the shells are brightly colored and have slightly charred. Turn off the heat, add a tablespoon of butter to glaze the shrimp and set aside.
To serve, give the risotto a quick stir and taste to adjust for seasonings. Spoon onto plates, and place a few shrimp onto each serving of risotto. Sprinkle with the remaining Parmigiano-Reggiano and freshly cracked black pepper, and drizzle with a touch extra virgin olive oil. Serve immediately.