Preheat the oven to 350°F. Grease a cookie sheet, then slice the eggplant lengthwise. Place on the cookie sheet, cut side down. Bake for 20-30 minutes, or until the eggplant is cooked through and very soft. Remove the eggplant and cool enough to handle. Scrape the flesh away from the skin and puree it in a food processor or blender. You will need 1 cup of eggplant puree. If you have extra, reserve it for another use.