Place squash in a saucepan with enough water to cover. Bring to a boil, and simmer over medium heat until tender, about 15 minutes. Drain, and cool.
Preheat over to 350°.
In a blender or food processor, combine butternut squash, brown sugar, cornstarch, egg, milk and spices. Process until smooth. Pour into the unbaked pie shell.
Bake in preheated oven for 50 minutes, or until a table knife comes out clean when inserted in the center.
(optionally you can use a can of sweetened condensed milk and omit the sugar).