Chop up the onions, carrots and celery into evenly sized chunks. Give 'em a good sweat over medium heat in some oil. Cook for 10-15 minutes or until they are browning. You can optionally add a sprinkling of salt.
Add the remaining ingredients: ½ parsley bunch, 1 teaspoon black peppercorns, 3 tablespoons nutritional yeast, and 1 gallon cold water. Bring to a boil, then reduce heat to a simmer and partially cover.
Simmer for 60-90 minutes.
Strain the stock to remove the leftover veggies. I added a half teaspoon of salt at this point, but keep in mind this will only partially season the stock -- this will give you some leeway when using it in various recipes.
Portion into 2-cup or 4-cup sized containers (or use muffin tins for smaller portions). Freeze the portions you won't immediately need and store the rest in the fridge where it will keep for a few days.
