Put puff pastry sheets out to defrost for 40 minutes before you start. Preheat oven to 400 degrees Fahrenheit. Line baking sheet with parchment paper.
Begin filling by sauteing onions in olive oil until lightly browned.
Add ground beef to onions at medium heat. Stir until beef browns. Drain oil from pan, if there is any.
Turn heat to low. Add beef broth mixed with cornstarch, tomato paste, and spices (cumin, paprika, and cinnamon).
Mix well, then simmer until the sauce thickens (about 2-3 minutes). Add green olives, and, if you want, the hard-boiled egg.
Make sure puff pastry is fully thawed - if it's not, it will break apart and just not work quite right.
When you unfold the sheets, it looks like three columns; I cut the middle column in half lengthwise.
Put about two large spoonfuls of filling in the lower half center of the pastry. Think about using ⅛ of the filling per pastry. Leave about an inch around the sides for folding and sealing.
Paint the edge of the pastry with the egg wash for sealing. Fold the pastry and press down on the edges with the tip of a fork to seal so no filling will leak.
Brush the top of the empanada with the egg wash.
Repeat seven more times.
