Cha for Bun Bo Hue

In a frying pan, on medium heat, add oil and saute onions, garlic and whites of green onions. If mix looks dry then add more oil. Saute until fragrant, around 30 seconds to a minute. Remove from heat and let it cool.
In a food processor, add ground pork along with fish sauce, potato starch, mushroom power, sugar, ice cubes, baking powder and the fried onion mix.
Mix for 5 minutes until it looks pasty. Then hand mix in black peppercorns.
I like to remove then air pockets by taking out the meat mix and slamming it onto a cutting board. Repeat this process 10 times to remove as much air pocket as possible. This will make it more dense.
Place in fridge and let it marinate while you are making your Bun Bo Hue.
When your bun bo hue is ready, bring the pot of broth to a boil. Scoop the meat mix by the spoonful and add to boiling broth. You will know when the cha is cooked as it will float to the top.