White Chicken Stock

This recipe is from seriouseats.com. It appears to be a highly researched recipe from a professional chef who made many batches of stock, testing different types of chicken parts, ratios of water to chicken, whether to dice the vegetables, etc. Here's part of his writeup:

White chicken stock, in which neither the chicken nor the aromatics are roasted first, may be the most versatile of all stocks. It's also incredibly easy to make, leading to a deeply flavorful stock, with a method and ingredients that are as easy and accessible as possible. Requiring such a minimal investment of time and effort, this stock will upgrade any dish or sauce you make compared to the store-bought variety.

NOTE: 4 pounds of chicken for the 4 quarts of water here is the minimum I've found that will produce a good, flavorful stock; packing in even more chicken, up to 8 pounds per 4 quarts, will yield an even richer, deeper stock. Different parts of the chicken will contribute different amounts of gelatin to the stock. Breast meat produces a deliciously flavorful stock that is very thin, while wings produce a slightly less clean flavor with lots of gelatin. If, even after being fully refrigerated, your stock still looks thin like water, add the gelatin solution below. Feel free to add other herbs, such as fresh thyme or bay leaves.

Ingredients

4-8 pounds chicken parts, such as wings, bones, breasts, and legs (see note above)
4 quarts water
2 large yellow onions, diced
4 large carrots, diced
4 large celery ribs, diced
8 crushed medium cloves garlic
2 large sprigs parsley (see note above)
2 packets unflavored gelatin dissolved in 1/2 cup cold water (optional, see note above)

Instructions

Combine chicken, water, onions, celery, garlic, and parsley in a large stockpot and bring to a simmer over low heat. Lower heat, maintaining a very gentle simmer, and cook for 1 hour 30 minutes (he notes it isn't necessary to skim, in fact in his testing the skimmed broth wasn't as clear as the non-skimmed). Strain stock through a fine-mesh strainer, let cool, then transfer to containers and refrigerate until completely chilled, about 6 hours. Skim off and remove any fat and scum on the surface. Refrigerate for up to 5 days or freeze for up to 6 months. If stock is thin even after being fully refrigerated, add optional gelatin solution to stock and bring to a boil until fully dissolved, then refrigerate or freeze.