I’ve been making this for years, even before the heart attack, mostly because I’m too cheap to buy pre-made vegetable broth. I also do something similar with chicken.
I save all my vegetable scraps such as carrot peelings, celery ends, onion skins, garlic skins and ends, bell pepper scraps, ends from trimming cabbage, trimmings from tomatoes, broccoli stalks.
Belonging to a CSA farm, we get lots of veggies during the summer.
I put all the peelings in a Ziplock Freezer 1 gallon bag and save them in the freezer, and keep adding to the big bag until it’s full.
When I’ve gathered a couple of full bags, I take them out and dump them in the crock pot and fill with water (about 6 quarts), cover and set on LOW for overnight.
Allow to cool completely and ladle into a colander in it with a big bowl under it. Discard all the scraps in the colander.
Package up the broth into quart-sized Ziplock freezer bags, 2 cups per bag, canning jars or other freezable containers.
You can also freeze some of the broth in an ice cube tray. Pop out the cubes and put in a freezer bag, labeled and dated. Use these when a recipe calls for 1 to 2 Tbsp. of stock or broth.
To use this with chicken – I do all of the above and save chicken bones and parts in a separate freezer bag, When it’s time for the crockpot, I add the chicken to the veggies and cook overnight. Strain well!