Freakin' Cheap: Almost-Free Homemade Stock

Risottos, soups, and gravies taste best when they're made with homemade stock. I want to make these dishes quickly, but stock takes a long time to prepare. My solution is to make stock in bulk and freeze it.

My stock is basic, and varies from batch to batch depending on ingredients on hand. It provides a foundation of flavor and body.

I don't buy any of the ingredients specifically for stock, and I try to make the preparation as unfussy as possible.

Ingredients

I accumulate the ingredients in Ziploc bags in the freezer.

I use some or all of the following:

Onion
Carrot
Celery
Leek
Scallion
Fennel
Tough mushroom stalks
Chicken and turkey carcasses (with some meat left on)
Parmigiano Reggiano rinds

The vegetables are raw trimmings from the preparation of other dishes, or they had been starting to go past their prime. Relative quantities are not terribly important because I can adjust the flavor when I use the stock.

Preparation

My method is just about the simplest possible.

1. Tip the contents of the Ziploc bags into a large pot. Stock is a base for a dish, so I don't add any salt or other seasonings.
2. Add cold water up to an inch, or so, below the top of the ingredients.
3. Cover pot with lid.
4. Heat on stove top. Never allow the water to boil: keep the water below the boil with a single bubble rising every second or two.
5. Once they are thawed, compact the ingredients slightly.
6. If necessary, add hot water up to the top of the ingredients.
7. Maintain gentle heat below the boil. If I don't want to stand over the stove to make sure the liquid stays below the boil, I put the entire pot into a 200°F convection oven, as pictured at the top of this post.
8. After about 4 hours (2 hours is plenty if there's only vegetables), remove pot from heat, allow to cool slightly.
9. Transfer as many of the ingredients as you can with a perforated spoon to a colander set in a bowl (to catch some extra stock). 
10. Filter stock through a sieve.
11. Filter stock again, this time through cheesecloth sitting in a sieve.
12. Allow stock to cool.
13. When it's about room temperature, place stock in the refrigerator until fully chilled. (Overnight is best.)
14. Skim any fat from the surface of the stock. The stock is sometimes partially set up at this point.
15. Ladle stock into plastic containers and freeze. I use one-quart containers; you can also use ice cube trays.

I keep a jar of Better than Bouillon Reduced Sodium Chicken Base handy for the times I've run out of homemade stock. I think it's better than anything else I can find in a jar, box, can, or foil. Homemade is still best.