Mix all the ingredients for the steak marinade in a medium bowl then fully coat the steaks in it. Leave on the bench for an hour to marinate and allow meat to come to room temperature.
In a small food processor (eg NutriBullet) put in all the ingredients for the chimichurri except for the avocado oil and diced avocado. Blitz in the food processor until the leaves are roughly chopped. Pour in the avocado oil and blitz further until the leaves are finely chopped. Tip into a bowl then stir through the diced avocado. Marinate for at least 30 minutes in the fridge.
Once the steak has marinated, heat a pan or barbecue hotplate. Once very hot, put the steaks on and fry for a couple of minutes on one side to form a crust then a couple of minutes on the other side. Then flip for another minute on each side again until cooked to your liking. Rest the steaks for 5 minutes then slice it and dress with avocado chimichurri.
Serving Suggestion
Season with salt, pepper and extra chilli, serve with corn.