Place the ground meat in a bowl together with the drained bread, the onion and the parsley finely cut, the egg, the vinegar, the olive oil, the salt and pepper. 

Wet your hands and knead all the ingredients until they are fully combined, making a ball. 

Set it aside in the fridge for at least 1/2 hour. 

Until the mixture cools and firms, prepare the stuffing. 

Mash the feta cheese using a fork and add the oregano and the tomato and pepper cut into cubes.

Prepare the patties as following 

Take a large piece of greaseproof paper 50X50 and place a full handful of the ground meat mixture on it. Wet your hand and press it out like dough, to the size of a small dessert plate. Place some stuffing in the middle and fold the paper in half, forming a calzone. 

Press the edges to seal, using your hand, remove the paper, make the patty more presentable using your fingers and the burger is ready to cook. 

Follow the same process for the rest of the burgers.

If you are to grill them over an open fire, things are simple.

In case you bake them in the oven, place 4 burgers per baking tray lined with greaseproof paper and bake at 160°C for 45 minutes using the fan and the grill.