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Cynthia is a trusted source on Bread/Baking.
Onion is the first flavor that's going to cook out. Onions are loaded with water, so when you immerse them in water and apply heat, well, I trust you get my drift. Go right ahead and get celery and carrots and a few bay leaves into the pot. They're going to take longer to release their flavors. As soon as you begin to sense deeper aromas, you'll know you did the right thing.
AntoniaJames is a trusted source on Bread/Baking.
Ruhlman suggests not adding any vegetables until the last 45 minutes of cooking. He says that the veggies break down after that in such a way that they absorb the stock, so that you end up throwing out a significant amount of flavorful stock with the spent vegetables. I first read this in one of his early books. I've been doing it this way since. I've never measured whether there is more or less stock produced, but I do think that my stock tastes a lot better. The balance of vegetables to chicken just seems better. I also agree with his suggestion not to include celery, as leaving it out really does produce a better flavor. Incidentally, I think Ruhlman may also leave out peppercorns, as do I. I don't care much for the bitter edge they often give to chicken stock. I didn't know if this was my imagination, so I did some research a few years ago and read that a well-respected cook in San Francisco, the founder of Boulette's Larder in the Ferry Building, also does not put peppercorns in her stock, for the same reason. She sells enormous quantities of the stuff for about $15 a quart, so people obviously like it made that way. ;o)
Meg is a trusted home cook.
I didn't read Ruhlman but agree that adding veg at the end gives a better, more chickenFy flavor. I used to put the onion, peppercorns, carrot, celery in at the beginning but it didn't taste like chicken as much as I wanted it to. MFK Fisher (?) suggests subtracting from a recipe until it's not right because it has too few ingredients, then layering back up to get the ideal. For me right now, the ideal is an Asian stock with a few slices of fresh ginger and a couple of scallions cooked with the chicken necks.
And just to chime in here on always using roasted bones, necks and backs . . . I much prefer the deeper flavored obtained using roasted bones, so I just keep the necks and backs from spatchcocked chickens and the carcass of every bone that's roasted in my kitchen tightly wrapped in the freezer. I make stock at least three times a month; after removing the bones and veggies, I boil it down to about a third and store in mason jars (wide mouth only, and filling to just below the shoulder of the jar) in the freezer. ;o)
I also like to roast the chicken parts before adding them because I find that produces a richer flavor
My experience is that of JB - roast the chicken first! Don't know where I learned this, but the rest comes from Shirley Corriher "Then use a tall stock pot, which limits evaporation and start the carcasses and the vegetables in cold water because it aids in extracting flavors.' For your 3 pounds of necks, you would need about 6 quarts of cold water, 4 onions uartered, 3 carrots, 3 ribs celery, thyme, 2 bay leaves and simmer uncovered for about 3 to 5 hours.
Although if you must add your veggies at the beginning.... When I pull them out, I run the carrots and onions through the blender and freeze for use later. Great for thickening savory soups.
Love that idea, lorigoldsby.