Roasting the vegetables yields rich and flavorful results.
- Preheat oven to 425°F.
- Combine carrots, onions and fennel in a large roasting pan. Toss with oil. Transfer half the vegetables to a second roasting pan. Roast the vegetables for 45 minutes, stirring every 15 minutes and switching the position of the pans each time you stir.
- In one pan, push the vegetables to one side and spread tomato paste in the other side. Continue roasting (both pans) until the tomato paste begins to blacken, 15 minutes more.
- Transfer the roasted vegetables to a large stockpot. Pour 1/2 cup wine into each roasting pan and bring to a boil over medium-high heat. Cook, scraping up any browned bits, for 1 to 2 minutes. Add the contents of the roasting pans to the stockpot, along with water, celery, parsley, thyme, peppercorns, garlic and bay leaves. Cover and bring to a simmer. Uncover and simmer for 1 hour without stirring, adjusting heat as necessary to maintain the simmer (if the stock boils it will become cloudy).
- Strain the stock through a colander, pressing on the solids to remove all liquid. Discard solids. Let the stock cool before storing.