Preheat oven to 180°c. Place a large sheet of foil, on a baking tray.
Make 5 cuts across the cobb loaf, cutting down to the bottom, but not right through. Turn and make another 5 cuts cross ways. Do not cut through the bottom crust (you want to be able to push filling into the cuts, but leave the loaf intact).
Heat butter in a frying pan and cook onion, garlic and bacon for 5 minutes until golden. Transfer to a bowl. Add 3/4 of cheese and parsley. Stir to combine.
Scatter mixture over the bread and push down into the cuts. Drizzle melted butter over the bread. Wrap the foil around the loaf to enclose. Bake for 15 -20 minutes.
Unwrap foil and sprinkle cobb with remaining cheese. Bake for a further 10 minutes or until cheese is melted and golden.