Though every chef has his or her own approach to whipping up delicious fare, all agree on certain basics. Chefs Russell Siu, Goran Streng and Kevin Hanney, who are each donating 10 gallons of soup for the Empty Bowl project on Friday, agree on one basic for cooking up a satisfying soup: Good soup starts with good stock.

Their tips:

»» Russell Siu (3660 on the Rise): To make a flavorful vegetable stock, use broccoli, cauliflower, tomatoes and mushrooms, plus fresh herbs such as thyme, basil and garlic. Cook slowly, on a low simmer, for 90 minutes to two hours, to avoid a cloudy broth.

»» Goran Streng (Tango): Start off with some kind of fat, whether bacon fat, oil or butter, then sauté vegetables as long as possible to caramelize, which brings out flavors. Then add stock. Homemade stock is best. Chicken, veal and beef stock can be reduced, then frozen in ice cube trays for easy use. Cook veal and beef bones for six hours or more; chicken should cook no more than an hour, skin off, then strain and reduce. Fish stock should be cooked just 20 to 30 minutes, and broth should NOT be reduced or flavor will be affected.

»» Kevin Hanney (12th Avenue Grill): Soups are a great way to get rid of everything in your refrigerator, but good stock is the key. While homemade is best, new chicken stocks on the market are also good. Look for organic, boxed stock low in sodium. Other tips: When adding grains, cook them separately and add just before eating. If you add them directly to the pot, they will absorb all the liquid.