Cut off pointed end of garlic just to expose cloves. Place garlic and next 5 ingredients (through turnips) on a large jelly-roll pan. Drizzle with oil; toss well. Bake at 450° for 10 minutes. Add leek and mushrooms. Bake an additional 35 minutes or until browned and tender, stirring occasionally.
Spoon vegetables into a Dutch oven. Pour wine into jelly-roll pan, scraping to loosen browned bits. Add wine mixture, 10 cups water, and remaining ingredients to vegetable mixture; bring to a boil. Reduce heat, and simmer 1 hour, stirring occasionally.
Strain through a fine sieve over a bowl; discard solids. Store in an airtight container in the refrigerator up to 1 week.