Take a large cooking pot and place cow trotters and chicken in it. Cover this with cold water.
Place the cooking pot on the burner at a high heat and bring it to boil. Once it starts boiling, remove it from the burner and drain the water.
Now wash all the bones thoroughly with cold water. Scrub any bits of coagulated blood or dark marrow until the bones are uniform grey or white.
In a frying pan, heat the cooking oil at a high flame. Add onions, garlic and ginger in the pan and toss them occasionally. Add a pinch of salt and black pepper too. Cook until they are almost blackened from both the sides. This may take about 15 minutes. Remove in a plate and set aside.
Once the bones are all completely washed up, place them again in the cooking pot. Add the blackened onions, garlic and ginger. Also add the white part of the scallions and the beef cuts in the pot. Fill it with cold water. Now bring it to a boil at a high flame. After some time, reduce the flame and cover the pot with a heavy lid.
Let it boil for around 4 hrs until the meat is completely tender. Keep checking on the pot after every 15-20 minutes.
Once the meat is tender, remove it with a spatula. Place the meat in a sealed container and refrigerate it for around 4-6 hrs.
After the meat is removed from the pot, cover the pot again with the lid and continue cooking. Cook until the broth gives a creamy and opaque appearance, this may take around 6-8 hrs.
Now cook the broth at a high flame until it gets reduced to around 3 quarts. Add salt and black pepper to enhance the flavour.
Once it is reduced, strain it in a clean pot so that all the solid bones are removed from the broth. Strain again through a fine mesh strainer in order to get a cleaner soup.
Now take the meat out of the fridge and chop it finely.
Add this meat in the soup and mix well.