Melt 2 tablespoons of the butter in a saucepot over medium heat. Toast the pasta in the butter until deep golden and nutty, and then transfer to a plate. Pour in a drizzle of EVOO and melt the remaining 1 tablespoon butter. When the butter has melted, cook the garlic and onions until softened, 5 minutes. Stir in the rice, coating with the butter, and sprinkle with the sage, salt and pepper. Pour in the wine, letting it absorb into the rice, and then add the stock and bring to a boil. Reduce the heat to a simmer and cook the rice, covered, until al dente, 16 minutes. Remove from the heat and fluff with a fork.
Cross-hatch the butternut squash flesh into 1/2-inch-wide scores. Dress with EVOO and sprinkle with salt, pepper and a little nutmeg. Drizzle with a little honey and roast, cut-side down, until the flesh is just tender enough to remove carefully from the shells, 15 to 20 minutes. Scoop the squash pieces into a dish, cut-side up, making sure not to break the squash shells.
Heat a drizzle of EVOO in a skillet over medium-high heat and brown the sausage, crumbling the meat as it cooks. Combine the cooked sausage with the pasta, rice and squash. Fill the squash shells with the stuffing, and top with a drizzle of EVOO. Top with the cheeses and bake until hot and browned, 30 minutes. Garnish with the toasted pine nuts and serve hot.
For a make-ahead meal, cool and store the stuffed squash shells without the cheeses. Bring to room temperature before topping with the cheese and baking.