A "Yooper" is from the Upper Peninsula of Michigan. Yooper=Upper.
Pastie is sort of like a meat/veg pie, but in turnover fashion. It can also contain dessert in one end of it. Typically it will contain cubed beef (round steak seems to work well), veg can range from diced potatoes to carrots to rutabagas to turnips. Also some onion, s/p to taste.
The dessert area, if you want to put some in one end, can be something like a pie filling.
They are typically cooked without any liquid inside them and are sauced at the table once cracked open with ketchup or brown gravy.
They were intended as a portable, hearty meal for the Cornish, from Cornwall U.K. miners. Hence the name, Cornish Pasties.
Here are some recipes