- In a bowl, mix together the marinade ingredients, then drop in your bavette. Set aside to marinade at room temp for at least an hour, turning in the marinade every 15 minutes or so.
- Meanwhile, add bacon or pancetta to a pan, allow the fat to render, then add the butter. When foaming, add onions and pepper and a little salt. Cook until translucent then chuck in the vinegar and sugar and allow to cook until rich and together, about 1 hour, topping up with water if necessary. Set aside to cool slightly.
- Prepare your grill for direct cooking, banking your coals to one side. Remove the steak from the marinade, and dab away any excess oil (to avoid flare ups). Grill for roughly 3 minutes on each side, brushing with a little or the remaining marinade. Transfer to the cool side of the bbq to finish cooking if not quite to your desired finish.
- Butter your bread and grill on the cool side of the bbq until nicely toasted. Rest your full steak on top of the grilled bread for at least 10 minutes.
- Slather both sides of the toasted baguette with the bacon onion jam and dab around the sandwich sauce.
- Slice the steak against the grain and load it on the base of the sandwich. Top with the dressed salad / parsley. Tuck in.