Bring a pan of water to the boil and cook the potato for 10-12 minutes, until tender.
For the monkfish, heat the oil in a pan.
Sprinkle the rosemary and salt and freshly ground black pepper on the monkfish and wrap in the pancetta.
Sear the wrapped pancetta in the pan for 4-5 minutes, or until cooked through.
To make the garlic oil, heat the olive oil in a pan and add the chilli, garlic and onion wedges. Heat for 8-10 minutes.
Drain the potatoes and transfer to a blender with the butter, seasoning and garlic. Blend until smooth.
To serve, spoon the mash onto a serving plate and top with the wrapped monkfish. Serve the garlic chilli oil alongside.