Mince 3–4 cloves of garlic finely. In a small bowl, mash the butter with the minced garlic until smooth, then stir in chopped green chillies, a pinch of chilli flakes, and a teaspoon of oregano. Add a tablespoon of water only if you need to loosen the mixture for easy spreading.
Slice the pav horizontally (leave the halves attached at the back if you like pull-apart pieces) and spread the garlic-herb butter generously over the cut faces.
Grate or tear the mozzarella cheese and pile it evenly over the buttered pav. Sprinkle a little extra chilli flakes if you want more heat.
Heat a wide pan over medium heat and add a thin film of oil or melt a bit more butter in it. Place the prepared pav, cut side down, into the pan and press gently with a spatula so the cheese contacts the heat and begins to melt.
Cover the pan with a lid for 2–3 minutes to trap heat and encourage the cheese to melt through; lift the lid to check that the bread is turning golden and the cheese is gooey.
Carefully flip the pav (cheese side up) and toast the outer crust until golden and crisp. Remove from the pan and drizzle a little chilli oil over the top for an extra flavor boost.
Scatter chopped coriander leaves over the warm cheesy bread, slice into portions and serve immediately while hot and stretchy.
