Lots of trimming to come (photo courtesy True Food Kitchen).  Stock, ready to use or freeze—or season it and enjoy a cup of broth (photo courtesy Good Eggs).  Plan B: Instead of stock, turn those trimmings into a purée of vegetable soup (photo courtesy Botanica | LA).
When we were quite young, a friend of the family was watching our mom cut vegetables for soup, and toss the trimmings. He had grown up on a farm in Sicily, and said: “We never threw away anything edible, not the smallest part. If we could have saved it, we’d have cooked the ‘oink’ from the pig.”
That’s how it’s been through history, except in affluent homes in affluent countries, whose denizens weren’t scraping for every bit to eat.
Modern cooks who want to minimize waste know that they can add flavor to homemade stocks by saving the carrot peels, celery leaves and trimmed ends, the last scrap of onion before the root, parsley and other herb stalks, wilted herbs, sprouted garlic and onions, the tops of scallions, and many vegetable trimmings.
Consider anything that isn’t rotten or moldy, or on the “Avoid” list below.
Limp vegetables? Stock. Herbs that have begun to yellow? Stock.
Wash and trim the vegetables as usual. Then set the trimmings aside and let them dry a little bit to remove moisture before you bag them.
Toss the ends, leaves, peel, roots and stalks into the same freezer bag—and feel good about not wasting money or contributing to a landfill. (If you’re planning to use them in a week, store in the produce drawer with the air pressed out of the bag.)
When you’re ready to make stock, plan for 2 cups of trimmings per quart of stock from vegetables.
And note that the venerable chef Jacques Pépin, an instructor at French Culinary Institute in New York City, always checks his students’ waste bins to see what they’ve thrown away. For him, scraps are more about flavor and less about thriftiness (although his wife has blocked the process at home; it drove her bonkers).
SAVE THESE TRIMMINGS
Ends: asparagus, celery, chard, green beans, spinach.
Green tops: beet greens but not the rest of the beet (it will color the stock red), carrot and just about any root vegetable.
Herb stems: cilantro, parsley (basil and mint stems are best reserved for pesto or chopped into salads).
Onion family: garlic, leeks, scallions and any type of onion.
Peeled skin: cucumber, eggplant, potato, summer squash and zucchini, winter squash (unless you like to bake them—our Nana sprinkled them with cinnamon as a snack for us kids).
Root vegetable trimmings: except for the bodies of beets (color leaches in) and turnips (not everyone likes the way it tastes in stock).
Stalks: celery, chard, fennel (we’ve never tried rhubarb).
Other trimmings: bell peppers, bok choy, corn cobs, green beans, lettuce, mushrooms, napa cabbage snow peas, sugar snap peas (we’ve never tried the pods of green peas).
AVOID: COMPOST OR TOSS THESE TRIMMINGS
What not to use: vegetables with very strong flavors:
The cruciferous group: arugula, broccoli, Brussels sprouts, cabbage, cauliflower, collard greens, horseradish, kale, kohlrabi, mizuna, mustard greens, radish, rapini (broccoli rabe), rutabaga, tatsoi and turnips. Ditto, artichoke trimmings (but the cooked stem is delicious to eat).
Anything that will color your stock, unless you don’t care*, such as beet, tomato or the papery skins of onions (they’ll turn stock brown) and garlic. But here’s what you can do with those skins.