Prepare Filling: Begin by blitzing the chorizo into a paste. In a heated skillet, sauté diced onion and minced garlic in olive oil until fragrant. Add the chorizo and ground beef, cooking until browned. Stir in tomato paste, spices, potatoes, and chicken stock; simmer for about 15 minutes until the potatoes are soft.

Cool Filling: Once cooked, remove the skillet from heat. Stir in chopped green onions and let the filling cool for at least 2 hours to maintain pastry flakiness.

Make Dough: In a food processor, blend all-purpose flour, salt, and cold butter until crumbly. Add egg yolk and warm milk, blitzing until a dough forms. Chill the dough for 30 minutes for easy handling.

Roll and Cut Pastry: On a lightly floured surface, roll the chilled dough to about 3mm thick. Use a round cutter to cut out 6-inch rounds, creating the pastry bases.

Fill and Seal: Spoon the cooled filling onto one half of each pastry round. Add sliced olives and hard-boiled egg if desired. Brush the edges with egg white for sealing, then fold over and crimp the edges to secure the filling.

Bake: Preheat your oven to 220°C (425°F). Place the empanadas on a baking sheet lined with parchment paper. Brush the tops with egg yolk and bake for about 20 minutes or until golden brown and crispy.

Serve Hot: Let the empanadas cool slightly before serving. Enjoy them with dipping sauces like chimichurri or avocado sauce for an extra burst of flavor!