Combine the melted butter, olive oil, onion, garlic, mustard, poppy seeds, parsley and salt in a bowl.
Slice the bread on the diagonal in two directions, creating cubes of bread but DO NOT cut all they way to the crust.
Create a foil collar for the bread to help keep the side pieces in place.
Using your fingers, carefully spread open spaces along cuts and pour the butter mixture down into the cracks and spread some over the top of the bread.
Repeating that same technique, open the cracks and fill them with the grated cheese; stuffing it down inside. Seems like a lot of cheese. Hell yes!
Wrap the entire loaf with foil allowing room at the top to keep from having the cheese melt to the foil. Seal well around the outside.
Bake for 20 minutes then remove from the oven and unwrap.
Bake for another 10 minutes or until the cheese is melted and gooey.
Eat with fingers or fork; garnish with lots of napkins.