1. CLOSE YOUR MOUTH AND BREATHE THROUGH YOUR NOSE.
This will make you realize you CAN breathe just fine and immediately stop the panic.
2. WHILE BREATHING THROUGH YOUR NOSE, gently try to push the food item back up into your mouth, or swallow it if you can.
I figured this out while living alone. I would panic when I felt myself choking. It works like a miracle, because it is usually a spasm in the upper throat, near your mouth, and not a closed off pharynx that causes coking sensationss. You just have to understand that you CAN still breathe through your nose and that will end the panic. Once the panicky feelings are over, everything is easier to deal with and you can usually spit out the food or even find a way to swallow it. But at least you realize that you are not imminently going to die, which is a good thing to know.
Hope this advice helps someone. If it does, I would love some feedback. I have offered it to friends, and they have loved it, found it useful too, so I know it works.
Best wishes to all,