Prepare the Dough: In a large bowl, mix the lukewarm milk, sugar, yeast, and melted butter. Stir until combined.

Add the all-purpose flour and salt, mixing with a spatula until a soft dough forms. If the dough is too sticky, add a little more flour; if too dry, add a bit more milk. Aim for a slightly sticky dough rather than a dry one.

Transfer the dough onto a work surface and knead for about 15 minutes until it becomes smooth, elastic, and passes the "windowpane test" (stretching the dough without tearing).

Shape the dough into a ball, place it on a lined baking tray, cover with plastic wrap, and let it rise in a warm place for 1 hour (such as a preheated oven that’s turned off).

Prepare the Topping: In a small bowl, combine the room-temperature butter, egg yolk (if using), sugar, salt, mashed garlic, and chopped green onions. Mix until smooth and creamy.

Assemble the Bread: Once the dough has risen, gently flatten it with your fingers into a round shape, about 20 cm (8 inches) in diameter and 2.5 cm (1 inch) thick.

Use a sharp knife to score the surface deeply, creating a lozenge (diamond) pattern.

Spread the prepared topping evenly over the surface of the dough, ensuring it seeps into the scored lines. Pass the blade through the scores again to redefine the lozenge pattern.

Insert the thin strips of Mozzarella cheese into the scored lines.

Bake: Bake in a preheated oven at 180°C (350°F) with upper and lower heat (no fan) for about 15 minutes or until the bread is golden and the cheese is melted and bubbly.

Serve: Serve immediately while warm, allowing everyone to pull apart the cheesy sections.