Re:Italian Sausage on a Cart....
I have a local sausage maker make three different sausages for me. I have a different "Sausage of the Week" each week. That really keeps my customers interested. They check in each week to see what the special will be.
The sausages come from the butcher shop raw, but frozen. In my commissary, I heat to the proper internal for pork sausage by simmering water, then quickly place in ziploc bags and then directly to the freezer. I take out what I think I'll need for the day, and place in my meat cooler along with my other dogs, and sausages. You should NOT take raw sausages to your site. It's against most health department's rules to deal with raw meat on your cart. Cook them at you commissary, freeze or refrigerate. Heat them to 165 on a grill (if allowed) or a steam pan on your cart.
Please check with your local health department on how to deal with raw meat at your kitchen/commissary. Hopefully they will allow you to do the par-boiling there, bu be prepared for them to tell you that you must use a full commercial kitchen, not just a regular cart commissary. The one thing that would be unheard of, would be them allowing you to cook raw meat on the cart.
I hope you are able to find a way to serve a good quality Italian sausage. Customers love them!