• To make the pastry in a food processor: Add the flour and salt, pulse to mix. Add the butter and egg. Pulse. While the processor is running add the water 1 tablespoon at a time until it starts to come together and form a ball.
• To make the pastry by hand: Add the flour, salt and butter to a large bowl. Using your fingertips (or a pastry cutter) rub the butter and flour until it resembles breadcrumbs. Drizzle in the water and mix using a fork until the it starts to come together and holds together when pressed in your hand. You may not need all of the water.
• Turn out onto a floured surface, form into a smooth ball, flatten and wrap with plastic wrap. Refrigerate for 30 minutes.

Make the chimichurri sauce:

• Mix all the ingredients except oil in a bowl, then whisk in the oil. set aside.

Make the filling:

• Add vegetable oil to a large sauté pan over medium heat until the oil ripples. Add the mushrooms and cook, stirring often until the start to brown. Add the beef, onion, carrot, salt and pepper and cook while breaking up the meat until browned. Stir in the garlic, cumin and oregano and cook for 2 minutes. Stir in the tomato puree and simmer for 5 minutes until thickened.
• Remove from the heat and stir in the olives. Transfer to a bowl and allow to cool to room temperature.
• Line a large baking sheet with parchment paper.
• Preheat oven to 350°F/180°C.
• Roll the dough to 1/8 inch thick. Cut out 6 inch circle. Place a small amount of meat into center of dough circle, brush egg wash around edges and fold in half. Press edge with a fork to seal.
• Line them all up on the baking sheet and brush all over with egg wash.
• Bake for 25-30 minutes or until golden brown.