Slice the onion and sauté until golden brown. Set aside on a plate. Sear the ground meat in a frying pan and add the four-spice mix, salt & pepper.
Add the sautéed onions and chopped tomatoes and simmer. Cook a hard-boiled egg and chop finely.
Once the meat mixture is cooked, remove from the heat and add the chopped hard-boiled egg and pitted olives cut into quarters.
Mix thoroughly. Cut the puff pastry into 10 cm circles.
Place some of the mixture in the centre of each circle. The idea is to fold one side of the circle over to form a semi-circle. Place the half-moon empanadas on a baking sheet and moisten with water or olive oil. Seal the edges of the empanadas with the prongs of a fork.
Brush the empanadas with egg yolk to give the pastry a golden colour when cooking.