This is a pork bone broth usually used for making ramen, though you could just drink it straight up and it'd be delicious too. The broth should be a light beige or white color rather than a darker brown color, and it should be very cloudy from all the fat particles and gelatin that have been rendered out.
Add pork bones to an 8 quart stock pot or instant pot and cover them with cold water
Set your stove or instant pot to high heat and bring the water to a boil
Once the water is boiling, remove the stock pot from the heat and strain the trotters using a colander
Wash your stock pot or prepare a second pot
Thoroughly wash each pork bone under cold water, with the goal of removing most of the meat and any bits that are red or brown in color, then return each bone to the clean pot
Cover the bones with fresh cold water
Set the pot to saute mode on high heat, and bring the water back up to a boil
Allow the bones to boil for 30 minutes or so
Add the onion and garlic to the mixture, then place the lid on the pot and set to soup mode under high pressure and set the timer to 90 minutes
Turn off the pressure cooker and wait for the pressure to drop to the point that you can open the lid again
At this point, the bones should have released most of their gelatin and should be falling apart
Bring the liquid back to a boil over medium saute mode and boil for another 30-60 minutes. This will help to agitate some of the fat out of the bones and form that nice cloudy color
Remove all the big pieces of bone and onion, then strain the broth with a fine mesh strainer into a second vessel
Bring the bones up to a boil over high heat
Add the onion and garlic, then reduce the heat to medium and try to keep the mixture at a very low rolling boil
Cover the pot and cook for up to 10 hours. The longer the stock is left boiling, the more gelatin can be extracted from the bones
Remove all the big pieces of bone and onion, then strain the broth with a fine mesh strainer into a second vessel