"These terrific little meat pies are often referred to as Australia's national food. Great for munching on during sporting events, or just for a fresh new dinner idea. Cool pies well before serving, as filling will be very hot. Eat by hand or with knife and fork, as desired."
Preheat oven to 400 degrees F (200 degrees C). Grease a 12-cup muffin tin.
Heat a large skillet over medium-high heat. Cook and stir ground beef and onion in the hot skillet until meat is browned and crumbly, 5 to 7 minutes. (Drain and discard grease.) Add 3/4 cup water, ketchup, Worcestershire sauce, bouillon cubes, oregano, and black pepper. Bring to a boil, reduce heat, and simmer until combined, about 10 minutes.
Mix 1/4 cup cold water and cornstarch together in a bowl to form a paste; stir into meat mixture. Cook until thickened, about 5 minutes more. Remove from heat.
Use a 4-inch biscuit cutter to cut the pie crusts into 12 circles. Line each muffin cup with a circle, pressing into the bottom and sides. Fill each with the meat mixture. Use a 3-inch biscuit cutter to cut puff pastry dough into 12 circles. Top each filled muffin cup with with a circle and seal edges together. Brush pastry tops with beaten egg.
Bake in the preheated oven until crusts are brown and flaky, 15 to 20 minutes. Cool in pan before removing pies, about 10 minutes.