To make the smokey barbecue relish, place the onion and garlic in a food processor and process until finely chopped.
Heat the oil in a medium saucepan over a high heat. Add the onion mixture, bay leaves and chillies and cook, stirring, for 4-5 minutes or until the onion is soft. Add the mustard powder, paprika and salt and cook for 30 seconds.
Add the tomatoes, sugar, Worcestershire sauce, honey and vinegar and bring to the boil. Reduce heat to low and cook, stirring occasionally, for 20-25 minutes or until thickened. Discard the bay leaves and chillies.
Preheat a griddle pan or barbecue to high heat. Place the peppercorns in a mortar and pound with a pestle until crushed. Add the salt and mix to combine.
Drizzle the steaks with the oil and sprinkle with the peppercorn mixture. Cook the steaks for three minutes each side for medium-rare or until cooked to your liking. Set aside to rest for three minutes. Slice the steaks, top with the peppercorn mixture and serve with the barbecue relish.