Heat oven to 400 degrees F. Grease
Place squash cut-side down on oiled baking sheet and bake until the squash can be pierced with a fork (about 45 minutes). Let cool, then scoop out the flesh into a soup
pot, discarding the skin. Add vegetable broth
and water and simmer
uncovered, 30 to 40 minutes, stirring occasionally to break up the squash. Add salt and pepper to taste and, if too thick, add additional water or broth. Cool. Puree in food processor
or hand-held blender
until smooth, return to pot and heat. Serve drizzled with a ring of balsamic vinegar.