Mine isn't terribly traditional for Cornish pasties, but it's what my yooper family has always made...
I can give you some approximations and more details later if you need them.
You want enough butter tart pastry dough for 8 pies (single crust, that is...) Fanny Farmer's recipe for the butter tart dough is darned close to my Grandmum's. She says she uses the tart dough because it's nice and sturdy.
In a huge bowl, mix 1 1/2 to 2 lbs lean finely chopped or ground beef or a mixture of beef and ground pork. Put in about 4 cups potatoes, peeled and small cubed, 2 cups similarly prepared rhutabaga, 2 cups similarly prepared carrots, 1 very large onion, medium chopped, salt and pepper to taste.
Preheat oven to 425F.
Divide dough evenly into 8, 8" circles. Divide the filling evenly between the circles, placing the filling on one half of the circle. Fold the other half of the circle over the filling, and crimp edges firmly together with a fork. Slice a couple of slits into the top of each pasty to allow steam to escape.
Bake for about 1 hour. Serve with whatever you like. In the U.P., we served it with chow-chow, ketchup and/or brown gravy. Yum, yum, yum. It makes me want to put on some snow shoes, grab some hard cider and pull out the instruments.