In a large pan, drizzle olive oil over medium heat. Add the onions and cook, stirring occasionally, until softened.
Stir in the garlic and cook until just fragrant, 30 seconds to 1 minute. Add the ground beef, breaking up into small pieces, and stir until browned and cooked through.
Stir in the salt, cumin, paprika, and pepper. Cook for another minute, then remove from heat and stir in the parsley.
Preheat oven to 350˚F (180˚C).
In a medium bowl, whisk together yogurt, olive oil, milk, and egg until smooth. Brush a thin layer over the bottom and sides of a 9x13 inch (23x33 cm) baking dish.
Place phyllo sheets on work surface and cover with a cloth. Place one sheet of phyllo in the prepared baking dish. Gently brush with the yogurt mixture. Repeat with six phyllo sheets in all, brushing each layer.
Spread the cooked ground beef over the prepared phyllo sheets in baking dish. Place a phyllo sheet over the layer of ground beef. Brush with yogurt mixture. Repeat with the remaining phyllo sheets. Brush the top with more yogurt mixture.
If desired, top the pastry with a sprinkling of nigella or sesame seeds.
Bake in preheated oven until golden, about 40-45 minutes. Let sit for 10 minutes before cutting into squares and serving.