2) Sauce: Pulse the herbs and garlic in a food processor until coarsely chopped. Add 180ml oil, 60ml vinegar and salt and pepper, to taste, and pulse to make a soupy vinaigrette â€” it will look a bit creamy until it settles. Add more oil and/or vinegar if too thick. Set aside.
3) Preheat the grill to high. Remove the steak from the marinade and season with salt and more pepper. Grill, covered, until nicely charred and medium rare, 3 to 4 minutes per side. Remove from the grill and rest 5 to 10 minutes before slicing across the grain.
4) Relish: Brush the onions with some rapeseed oil and season with rub, salt and pepper. Grill the onions, turning, until charred and soft. Remove from the grill and chop coarsely. Chop again with the spring onions and then stir them together with the chilli, oil, vinegar, and salt and pepper.
5) Slice the baguette on a diagonal 1cm thick. Brush with oil, season with salt and pepper and grill briefly, until just starting to crisp. Top each piece with some sauce, a slice or 2 of steak, more sauce and some relish.