Heat oil in a pan, add onions and spices and stir for about 2 minutes. Add minced beef and stir until browned. Add olives and season to taste with salt and pepper, before leaving to cool.
Cut rounds out of the pastry with a medium-size circle cutter. Brush the borders with the egg. Place 2 tablespoons of the beef mixture in the centre of each circle, discarding excess liquid to prevent pastry becoming soggy.
Fold pastry in half over the filling and press the borders with a fork or fingers to seal tightly.
Place the empanadas on a baking tray lined with baking paper. Brush each with remaining egg to colour and then cook for 15-20 minutes.
Hard-boiled eggs and sultanas can also be added to the filling.