Blanch the broccoli in a saucepan of lightly salted boiling water for 2 minutes. Drain well and refresh under cold water. Drain again, pat dry and set aside.
Rub the beef with 1 tablespoon of the oil and season well with salt and pepper.
Heat a ridged griddle pan until very hot, add the beef and cook over a high heat for 2 minutes on each side. Remove and leave to rest for 5 minutes, then cut into thick slices.
While the beef is resting, reheat the griddle pan, add the sourdough bread slices and cook for 2 minutes on each side until lightly charred.
Heat the remaining oil in a wok or large frying pan, add the garlic and chilli and stir-fry for 1 minute. Add the broccoli and stir-fry for 1 minute. Stir in the vinegar and remove from heat. Combine with the beef and rocket in a large bowl.
Arrange the bread on serving plates, top with the beef salad and serve.