Wet a deep baking sheet with cold water. Thaw the puff pastry sheets. Roll out half the sheets and lay them on the baking sheet.
Spread the minced meat evenly over the pastry. Layer the ham slices on top. Finely chop the pickled cucumbers and onions, scatter them over the ham, then spread a mixture of mustard, ketchup, and oregano over everything.
Roll out the remaining pastry sheets and place them over the filling. Press the edges together to seal. Prick the surface all over with a fork.
Place in a cold oven and bake at 180 °C (356 °F) using convection for 40-45 minutes until golden. Serve warm with salad or let cool and serve cold.