Step 1

Place the pork bones in a large stock pot and cover with cold water.

Step 2

Bring to a rolling boil over medium high heat. At this point a huge mess of scum will form.

Step 3

Remove from heat. Dump the water and carefully rinse all the bones under cold running water.

Step 4

Return the bones to the stock pot. Cover the bones with cold water and bring to a rolling boil.

Step 5

Add the mushroom and onion and maintain a rolling boil for 12 hours, replenishing the water along the way. You want to keep the bones under water the whole time. It's best to cover the pot for this or you'll be adding water every 30 minutes.

Step 6

After 12 hours, remove the stock from the heat and cool slightly. Remove the bones with a slotted spoon and strain the stock.

Step 7

The stock will keep in the refrigerator for 2-3 days or can be frozen at this point.

Step 8

The broth is flavoured by the tare of your choice. There are two good one's in the tonkotsu ramen recipe.