Preheat oven to 350. Cut squash in half and put into a casserole dish. COver tightly with aluminum foil and bake about 1 hour. Removen from oven, cool, and remove the seeds and strings. Scoop out pulp from shell and place in a bowl. While squash is baking melt butter in a large saucepan over medium heat; add the onion and cook, stir occasionally for about 5 minutes. Stir in tomato and cook another 5 minutes. Add the squash, half of the chickpeas along with their liquid and the stock. Bring to a boil then remove from heat. Using a blender, puree the mixture untl smooth. Add remaining chickpeas, then season with salt, pepper. Heat through just before serving and garnish with heavey cream if desired.