I like to make what I call boiled bone soup. The leftover stripped chicken carcus is broken up and boiled with leftover veg and stuffing with some seasoning to produce a stock. I seive this, add the stock to the pan with fresh veg and the meat juices from the original roast chicken, then bring to a boil adding the left over chicken. After boiling I reduce the heat to a simmer. My problem is here, the chicken always seems to stick to the bottom of the pan and burns unless I stand there for 2 hours. Why? How can I prevent this?
Don't boil it.
You want a bare simmer when trying to extract the flavor from the bones. If you're boiling, you'll both run into the problems that you mention (sticking & burning), and you end up with a worse broth -- much of the flavor is in the smell of the soup, and boiling too hard will both destroy compounds you want and kick them into the air (and thus not in the broth/stock).
My normal procedure is:
- With either a good cleaver, or poultry shears,can crack the longer leg and thigh bones.
- Cover with cold water by an inch or so.
- Add whatever scrap vegetables you have. (whatever you have that's getting a bit sad looking in the fridge, but isn't to the point of being spoiled. I also have a bag in my freezer of vegetables that were past their prime).
- Heat the water 'til you see bubbling, then back off the heat to maintain a bare simmer.
- Cook for 2 to 4 hours, checking on it every 30 min or so. (Once you're more experienced, you may not need to check on it as often ... but you need to watch for the water evaporating too quickly or things starting to stick)
- Strain out the bones & vegetables.
Cool down the broth if not serving that day, put into smaller containers, and put in the refrigerator.
On the day you're serving it, add in whatever diced vegetables and/or meat and heat through. Adjust the salt & acidity if needed, and maybe add some herbs.
- For something starchy like stuffing, heat it through separately and put a scoop in the bottom of the bowl, then pour the hot soup over it. (to avoid it turning into complete mush)
Can you reduce the heat somewhat? It will take longer to get to a boil, but I find that once it is boiling the level of the burner doesn't matter as long as it is enough to maintain the boil (my stove does this around level 4 out of 9 on the element heat settings). A lid will help with this.
Another option may be to find a small rack that will fit into the bottom of your pot to elevate the carcass and keep it from the direct heat on the bottom of the pot. I cooked a whole turkey in my pressure canner and kept the rack under it to keep it off the bottom and that worked well. Perhaps the same will help you. Just make sure that it is food-safe. One meant for the oven may work well.