In a large mixing bowl, combine lukewarm water, milk, and salt. Gradually sift in all-purpose flour, stirring until combined. Knead for 2-3 minutes on a floured surface until smooth and elastic. Divide into 10 equal balls, cover with a damp cloth, and let them rest for 20 minutes.

Finely chop fresh spinach and onion. Massage chopped onion with a pinch of salt until it releases juices, about 2 minutes. Mix with spinach, adding hot red pepper flakes and black pepper. Optionally, fold in crumbled cheese for a creamy filling.

Heat a griddle over medium-high heat. Roll out each dough ball into a thin sheet, approximately 1mm thick, ensuring an even surface. Keep covered to prevent drying.

Spoon a generous portion of filling onto one half of the rolled-out dough. Fold the other half over the filling to create a pocket. Press and seal edges tightly to prevent leaks.

Cook on the hot griddle for 1 minute on each side until golden brown and crisp, brushing each side lightly with melted butter or oil. Cook in batches if necessary.

Stack cooked gözleme on a plate and cover with a kitchen towel to keep warm. Serve hot alongside salad or yogurt dip.