My canner is small and I don't like wasting any potatoes so I always measure mine as I cut them. I peel them, cut them into chunks and then drop them into the quart jar until it is full, then put those potatoes in the pan they are going to be boiled in. That way I don't boil more potatos than my little canner can hold.
Once I have the amount of potatoes I need, I cut up one onion. Doesn't matter how you cut it, just get it in the pot with the potatoes. You'll also need garlic. I put a big spoonful of garlic in the pot (a tablespoon maybe).
The potatoes are cooked for 10 minutes.
While it is cooking you can heat up your canner, get your jars ready and also heat to boiling another fairly large pot of just plain water.
These have to be canned at 10 lbs pressure for 40 minutes (quarts). Here they are fresh out of the canner.
These are great mashed, fried or just heated up and eaten.