Heat the olive oil over high heat and add the beef and onion. Fry until slightly browned and translucent.
Add garlic powder, paprika and salt and stir through.
Add ketchup, passata, mustard, worcestershire sauce. Remove from the heat.
Spread mayonnaise over one side of each slice of bread. Line a baking tray. Lay the bread slices mayonnaise side down, slightly overlapping, across the bottom of the lined tray. Top with the beef mix, cheese, jalapenos, then lay down another layer of bread slices- overlapping again-mayonnaise facing up.
Top with a sheet of greaseproof and weigh down with a tray.