Chicken – How to filter out unwanted particles in the chicken broth

There's several major reasons why meat and poultry can be tough:

1. Collagen: muscles exist to impart a force between bones, when they contract there must be a connection between that muscle and the bone or the muscle would not be able to do work. Collagen is a strong protein that is distributed throughout a muscle and connects to a tendon, allowing the muscle to distribute its' force to the skeletal structure of the animal. The more load a muscle takes, the more collagen is needed to distribute the force, and the tougher the meat is.
2. The animal was stressed before slaughter: if the animal was stressed before slaughter it will have lactic acid buildup resulting in tougher meat
3. Poor treatment after slaughter: Once an animal dies chemical changes happen that toughen the meat, and the correct treatment is needed to allow the meat to relax again. If that isn't done right you'll get tough meat
4. Freezing and thawing: freezing makes meat and poultry tougher

Collagen breaks down in the presence of heat and moisture, so a long stewing at low temperature could make your chicken tender. The collagen helps make your broth thicker and taster too! That would take a maximum of 2-3 hours on a low simmer. If it isn't tender by then it isn't tough because of collagen and there isn't much you can do. If you've got a chicken that was stressed, not processed correctly, and then frozen there's a limit to how tender you'll be able to get it. You can try cooking it a couple more hours, but if it isn't tender by then it never will be.

You don't need to add any water to the slow cooker whatsoever. Your recipe is somewhat similar to the one that I use to cook my lunches but the quantities seem larger than mine, much larger. I assume that you chop everything up into small piece, including the chicken. The slow cooker should not be more than 3/4 full, so reduce your amounts if the quantities are too big.

Chicken breast doesn't need more than three hours on the 'high' setting in order to cook (six hours on low); this cooking time leaves most of the vegetables crisp (courgettes and pumpkin soften, but bell peppers, carrots and onions retain their texture).

Running a kosher kitchen, I would not know about adding cheese to the food, but anyway I would recommend adding the cheese to the food prior to serving, not while it is being cooked.

If you wish to separate some of the vegetables, one technique which I have used successfully is to put these vegetables in a wire tray (I use the plastic punnets in which we buy fresh mushrooms): these vegetable are cooked like the rest but are kept separate.

If you do wish to add certain vegetables after you have already started cooking, then you are supposed to add 20 minutes to the cooking time (every time one opens the lid of the cooker, steam escapes and it apparently takes 20 minutes to obtain the same amount of steam).