Cut the fat into small cubes by hand (5 mm x 5 mm) and blanch in boiling water for 2 minutes. After 2 minutes rinse in cold water.
Candy the blanched back fat by adding sugar to a small bowl, next add a layer of blanched fat, top it with a layer of sugar. Repeat this process till you are out of back fat. Cover and let it rest on your countertop for at least 3 hours
Cut your beef into small cubes and chill it. The temp of your meat should be just above freezing.
In your food processor (with sharp blades) add the meat, the rest of the ingredients and 1/3 of the water. Chop your meat for 30 -45 seconds.
Open the lid and scrape down the sides, add another 1/3 of your ice cold water and continue to chop fo 30 seconds more
open the lid one more time, add the potato starch and the rest of the ice water, continue to chop till your meat has turned into a smooth meat paste (farce)
Mix the candied pork fat with the meat and form into a roll. Slam the roll several times on the counter to remove any air pockets, then reform into a roll.
Wrap the Cha Bo in banana leaves or stuff it tightly into a 70mm casing.