We start with our feta sauce. Place in a blender the feta cheese along with the milk, the 3 tbsp of olive oil, the fresh oregano and the lemon juice. Blend until a nice sauce is created, while is nice to have small bits of the feta. If too thick add some more milk or even some of the water brine from the feta cheese to adjust.
Prepare your coals and once well rested and having created a nice grey ash spread them all over your grill and allow to rest.
In the meantime, put the meat cubes on skewers snugged next to each other but not too tight with pepper and onion squares in between them.
Place your skewers on the grill above the direct fire cook for about 15', until they get a nice gold to burned colour while brushing them with the olive oil and oregano mixture.
Just before they are ready sprinkle over them the salt and the sumac (optional) and place the pitta bread on the grill to get a bit charred, while basting them with the olive oil and dry oregano mixture.
Serve in a plate mixed with the cucumbers, tomatoes, parsley and red onions, next to the feta sauce.