In a large mixing bowl, combine lukewarm water, milk, and salt. Gradually add flour, stirring until a shaggy dough forms. Knead for 5-7 minutes until smooth. Cover and let rest for 30 minutes.

Finely chop spinach and onion. Sprinkle onion with salt and massage to release juices. Combine spinach with onions, black pepper, hot red pepper flakes, and crumbled cheese. Mix well and set aside.

Divide dough into 4 pieces. Roll each into a thin disc about 12 inches in diameter. Keep covered with a towel to prevent drying.

Place filling on one half of dough disc, fold over, and seal edges. Crimp with a fork to secure. Repeat with remaining dough.

Heat a large pan and add butter or oil. Cook each filled gozleme for 3-4 minutes on each side until golden and crispy.

Transfer to a plate and cover with a towel to keep warm. Serve immediately with yogurt dip or salad.