Place onions on bottom with bone marrow on top. Throw in large chunks of vegetables if you wish, adds more flavor.
Sprinkle in garlic, apple cider vinegar and all spices. Pour in water.
Seal lid and steam valve and set to high pressure for 90 minutes followed by a natural release.
Put a metal strainer inside a large pot in the sink. Use pot holders to lift inner liner of pressure cooker out and pour into the strainer so the pot catches the liquid.
You could collect the bone marrow and put into a jar for spreading on toast, or throw everything in the strainer away.
Pour liquid in your pot into large mason jars. Set on countertop until completely cooled with the tops off.
Set into fridge, covered, when cooled for a few hours. Take out and use a spoon to scoop and discard the layer of fat at the top. Seal tight and use within 4 days.