Make the pickled chilli paste by using a mortar and pestle to pound the chillies and salt to a paste. Stir through the vinegar.
In a small bowl, add 2 tablespoons of the pickled chilli paste along with the remaining marinade ingredients. Stir until well combined. Place 2 tablespoons of the mixture into a small bowl to use as a finishing sauce. Pour most of the marinade over the steaks (leave a couple of tablespoons for basting). Set aside to marinate for at least 10 minutes or overnight.
Heat a frying pan, grill plate or barbecue plate over high heat. Lightly coat with oil. Then cook steaks 2-3 minutes each side or until cooked to your liking. Baste the steaks with reserved marinade as they cook. Transfer the steaks to a plate and rest for 5 minutes before slicing.
To serve, mix the remaining 2 tablespoons of marinade with the coriander and spring onion. Drizzle the mixture over the sliced steaks. Mix the salad leaves with the sesame oil and lime juice. Serve salad with the steaks.