In a medium bowl, whisk together 1/2 cup flour, sugar, warm milk, warm water, and dry yeast until smooth. Let the mixture sit for 5–10 minutes, or until it becomes foamy and bubbles form on the surface.
In a separate large bowl, combine the remaining 4 1/2 cups flour and salt. Add the olive oil, Greek yogurt, and the activated yeast mixture.
Mix until a shaggy dough forms, then knead for 8–10 minutes, either by hand or with a stand mixer fitted with the dough hook, until the dough is smooth, soft, and elastic.
Lightly oil a large bowl and place the dough inside, turning it once to coat. Cover with plastic wrap and let it rise in a warm place for about 2 hours, or until doubled in size.
Punch the dough down, then transfer it to a lightly floured work surface. Divide it into 8 equal pieces and shape each into a ball. Cover loosely with plastic wrap or a kitchen towel and let them rest for 20 minutes.
Lightly flour the work surface, sprinkle a little flour over each dough ball, and shape it with your fingers or roll with a rolling pin into a roughly 7-inch (18 cm) circle.
Heat a large cast-iron skillet or heavy-bottomed pan over medium-high heat. Place one pita in the hot pan and cover with a lid for the first minute to help trap the steam and cook the inside. Cook for 2-3 minutes, or until bubbles begin to form and the bottom develops golden-brown spots.
Flip the pita and cook for another 1–2 minutes, until the second side is lightly browned and the pita is cooked through.
As each pita finishes cooking, place it directly into a clean kitchen towel set on a plate. Wrap the towel completely around the pita so it's fully covered. This traps steam and keeps the pitas soft. Enjoy!