Place the squash cut side up on a baking sheet. Place 1 tablespoon butter in the hollow of each half. Sprinkle with salt and pepper to taste. Cover the squash with a sheet of aluminum foil tucking in the edges.
Bake squash in preheated oven until tender and easily pierced with a fork, 45 to 65 minutes.
Scoop the cooked squash into a bowl, and mash until smooth. Mix in the allspice, nutmeg, cinnamon, and Parmesan cheese until well blended. Season to taste with salt and pepper.
Fill a deep pot with lightly salted water and bring to a boil.
To make the ravioli, place a wonton wrapper on a clean, flat surface. Brush edges with the egg white. Place about 1 tablespoon of the squash mixture in the middle of the wonton. Cover with a second wonton wrapper. Repeat with remaining wonton wrappers and squash mixture until all have been used.
Drop the ravioli into the boiling water, and cook for 3 to 5 minutes, or until tender. Remove, drain, and keep warm until sauce is prepared.
To make the sauce, melt the butter in a skillet over medium heat. Stir in the sage. Continue to cook and stir until the sage is crispy but not browned. Add salt and pepper to taste. Place 6 to 8 raviolis on serving plates, and drizzle with sauce.