Preheat oven to 350 degrees F.
Thaw and partially cook the carrots by microwaving them on high, together with the butter, for 90 seconds; set aside.
In a non-stick skillet over medium heat, brown the ground beef; when the meat is about halfway cooked, add the onion, garlic, and carrots, and sauté until beef is completely browned, about a total of 7 to 10 minutes; drain drippings, if any.
In a bowl, combine the beef mixture, cubed potato, and cheeses (and curry powder, if using), then season to taste with salt and pepper; stir well.
Place one of the pie crusts on a lightly-floured board, then mentally imagine the crust divided into 4 equal pieces: place about 1/2 to 3/4 cup of the cooked meat mixture in each equal quarter of the crust- make sure to leave about a 1/4 inch aisle beside each mound of mixture (the aisle should basically be the lines which divided the crust into 4 equal pieces, plus the outside edge).
Moisten the uncovered"aisles" and outside edge portions of the crust with water or milk, then place another crust over the top of it all and carefully press it down onto the exposed bottom crust areas (the"aisles" and outside edge), making sure that the mounds of meat are covered by crust.
Cut the 4 pasties away from each other down the middle aisles; using a fork, press the edges all around each pastie to make sure edges adhere.
Repeat the assembly process with the remaining crusts and meat filling.
Place the pasties on a lightly pan-sprayed non-stick baking sheet (4 should fit per large baking sheet, you might need to cook in two batches) and bake at 350 degrees F until crusts are golden brown, about 30 minutes.