Freeze your ingredients for an hour (just to get them really cold) and refrigerate your grinding parts (sounds crazy but it makes a big difference with the grinding). Cut the pork and chicken into 1-inch cubes.
Place all of the ingredients into a large bowl and stir to combine. Refrigerate this mixture while you set up your meat grinder.
Using a meat grinder, coarsely grind the mixture. Send the mixture through the grinder slowly, so that you do not create a jam.
After sending all of the sausage mixture through the grinder once, grind it using the coarse grind plate a second time.
You can shape the mixture into sausage patties at this point, if you would like. I'm not doing the whole casing thing at this point — just patties which then I break off pieces for the pizza sausage bites.
I like to pre-cook the sausage a bit before putting it on the pizza. Heat 4 – 5 tablespoons of olive oil in a frying pan, and fry the sausages over a medium heat until they are light golden on all sides. This will take about 7 mins. They will cook all the way through when you cook your pizza.