Slow Cooker Pumpkin Butter

1 cup white sugar

2 tablespoons ground cinnamon

1 tablespoon ground cloves

½ teaspoon ground allspice

1 (5 pound) fresh pumpkin - seeded, peeled, and cut into 2-inch cubes

Combine the sugar, cinnamon, cloves, and allspice in a bowl. Place about 1/4 of the pumpkin into the bottom of a slow cooker, and sprinkle with 1/4 of the sugar mixture; repeat layers 3 more times. Cover the slow cooker, set it on Low, then cook for 8 hours or overnight. Stir once or twice during cooking. When the pumpkin is a dark, golden color, place an immersion blender into the slow cooker, and blend the pumpkin butter until smooth.