Chop up the bones if necessary so that they can fit in the pot. Place the bones in a pot and add in enough room-temperature water to cover them by at least 1 inch.
Place the pot over the highest heat and bring to a boil. Keep the water on a rolling boil for 5 minutes. All the scum will rise to the surface. Discard the water and rinse the bones.
Transfer the rinsed bones into the largest stock pot you have - (mine is about 6 litres). Add in the onion, spring onion, ginger, garlic and carrot tops and ends. Add in room-temperature water until the pot is full. Bring the water to a boil, then turn the heat down to a simmer.
Cover the pot and simmer for 4 to 8 hours (I usually simmer for 6) - bubbles should break through the surface of the water gently while simmering. If it doesn't, the heat is too low and should be adjust higher. Stir the stock every hour to make sure nothing sticks to the bottom of the pot. If your stock pot is small and you need to top up with water, always top up with boiling water.
Strain the stock into a large clean bowl / pot. Let the stock cool completely to room temperature, cover then store in the refrigerator overnight.
The Next Day
Remove the bowl of stock from the refrigerator - the white layer on top is fat that should have solidified in the refrigerator. Scrape off as much fat as you can with a spoon (the fat can be used for cooking / stir-fries. Store the fat in a container in the refrigerator and use within 3 days).
If the stock has been simmered long enough and correctly, it should be in a gelatinous state as the collagen from the bones have been extracted, which causes the stock to gel. Divide the stock into containers of various sizes and freeze until needed.
- Chicken: Use carcass and bones like neck, feet, back bone. Chicken wing tips can also be used. - Pork: If no pork bones are available, you can use pork trotter instead. - Save the bones from your meals - store them in a ziploc bag and freeze them until you have enough to make stock. - If using bones from roasts (like roasted chicken), skip Steps 1 and 2. - I usually make stock with a mix of chicken and pork bones/carcasses. The taste of beef stock may be quite strong, so I only make it when I'm making a beef-based dish, like pho. - I usually freeze my stock in 1/2-cup (125 ml), 1-cup (250 ml) and 2-cups (500 ml) portions. 1/2-cup portions are good to make sauces, 1-cup portions are good for stews and when I'm cooking for 1 person while 2-cup portions are good for soups and noodle soups for 2 people.