Preheat the oven to 200°C (400°F) and line a baking sheet with parchment paper.
In a bowl, mix the cooked bacon, chopped boiled eggs, spring onions, minced garlic, pickled cucumber, parsley, shredded cheese, Greek yogurt, and crumbled feta until well combined.
Roll out the puff pastry sheets on a lightly floured surface and cut them into squares or circles.
Spread a thin layer of ketchup on each piece of pastry, then add a spoonful of the prepared filling in the center.
Fold or roll the pastry over the filling, sealing the edges. Press with a fork for a decorative touch.
Brush the tops with egg yolk and sprinkle with oregano.
Bake for 15–20 minutes or until golden brown and crispy.
Let cool slightly before serving. Enjoy warm or at room temperature!