Heat a small frying pan and add the pistachios. Toss in the pan for 2-3 minutes until lightly toasted. Immediately transfer to a small bowl and leave to cool slightly, then roughly crush. Set aside.
Bring the steaks to room temperature. Rub 1 tsp of oil into the steaks and season. Heat a large griddle pan on a high flame until hot, then reduce the heat to medium. Add the steaks to the pan and cook for 3 minutes, then turn over and cook for a further 2 minutes. Transfer to a plate and leave to rest.
Meanwhile, prepare the dressing. In a food processor, add the vinegar, orange juice, garlic and chilli flakes. Whizz together, then slowly drizzle in the rest of the oil until it emulsifies. Add the herbs and plenty of seasoning, then pulse until the herbs are finely chopped and the sauce is pourable.
Slice the steak diagonally and toss with the kale, orange and avocado. Scatter the pistachios over the salad and serve drizzled with the dressing.