Often the trimmings from vegetables are removed because they have a different texture. Some of these trimmings are perfectly edible (potato and carrot peels) while others are too fibrous to eat by themselves (leek leaves and parmesan cheese rinds). Either way these scraps can be used to make a wholesome, tasty broth. Broth is made by boiling a base (vegetables, meat or bones) until the essence leaches out into the liquid, leaving only a spent fibrous carcass behind. It is really an ideal use for scraps; the pieces of the vegetable with objectionable texture can still be mined for flavor. I keep a quart sized bag in my freezer and add my vegetable scraps to it until the bag is full. Then it’s time for a new batch of broth.
To make broth:
Collect your broth ingredients: I don’t follow any particular recipe for the amount and types of vegetable scraps, I just use what I have and add other elements if I think that the flavor is lacking in some respect. Generally, I like so see a good mix of root vegetables, herbs or spices and something with a solid, earthy-savory structure (either parmesan cheese rinds or mushroom stems work well for this role). Whatever else I have, I always add in a whole onion and a few garlic cloves. If you don’t have one of these groups, you can improvise and add things to round out the flavor. Use a base of 1 part vegetables to 2 parts water. I typically make two quarts of broth at a time, but you can certainly make larger batches. I do not salt my broth, but prefer to add salt later to suit the dish.
Boil the Broth:
Place all of your scraps and your water a large saucepan or stock pot. Cover. Bring to a full boil. Reduce heat and boil until all of the vegetables are limp and beginning to fall apart (about an hour) Strain.
At this point you can either cool and store your stock as-is or further reduce it to concentrate the flavor. I like to reduce the stock and then freeze it in an ice cube tray. Once frozen, the broth cubes can be conveniently stored in a freezer bag, and you can defrost whatever amount you happen to need.
Scraps to Save for Making Broth:
parmesan cheese rinds
stems of parsley or cilantro, or wilted, sad-looking parsley or cilantro
skins and trimmings from root vegetables (potatoes, carrots, parsnips)
the root end of onions (left over after chopping the rest of the onion)
the tough leaves of leeks
celery leaves and trimmings
Extras (amounts are based on 2qts of broth):
cumin seeds- 1T
coriander seeds- 1T
bay leaves- 3-5
black peppercorns- 2t
whole garlic cloves- 2-4
dried mushrooms- handful