This is a traditional English meal which was probably originally made with a much tougher pastry so that farmers and workers could just slip it into their pocket to eat cold at lunch time. Nowdays it makes a tasty dinner or lunch either hot or cold.
1 lb ground beef
1 medium potato (or half a large one)
1 medium onion (or half a large one)
1 tsp salt
puff pastry sheets, store bought frozen sheets are fine as long as you check they're not sweetened. Pepperidge Farm brand works well if you're in the US. (Or make your own pastry!)
Place the ground beef in a large mixing bowl. Peel and dice the potato and the onion. You can vary the relative proportions of potato and onion to beef depending on your taste, pretty much any proportion will work. Mix the potato, onion, and salt into the beef. You can do this with a spoon, but with your hands is easier and more efficient if you don't mind handling raw meat. It will end up looking something like this:
Lay the pastry sheets flat and use a small plate or bowl to cut circles out of them by running a sharp knife around the edge of the plate. If you're using store-bought flaky pastry sheets, you should be able to use a small bowl to cut two circles out of one sheet, aligned diagonally, and then put together two large triangles of the remaining pastry to make a large enough piece of pastry to cut a third circle. When working with flaky pastry, it's important to keep it as cool as possible, and not stretch it or pull it, as too much stretching can make it shrink or deform during cooking.
Lay the circles on a cooking tray, preferably on a sheet of parchment paper or similar to prevent sticking. Place a spoonful of the meat mixture on each circle.
Run a damp finger around the outside of the circle to make it slightly sticky, then fold in half and pinch the join together so it sticks closed and makes a little packet. With a sharp knife, cut a small slice in the pastry on each side to allow steam to escape.
Once the pasties are all made, place them in a 425 F oven for about 30-40 minutes, until the crust is just starting to brown. You can leave them flat on a sheet of parchment paper, or sit them on a metal cooling rack, which will allow the undersides to cook more crisply.
Can be eaten hot or cold. Yum!