Dice off the fat from the steak.
Take the fat cuttings and place them in a non-stick frying pan with the garlic cloves on low heat. Leave the garlic unpeeled for this step. Be sure to turn them regularly to cook them on all sides. Keep cooking until the fat crisps.
Peel sweet potatoes and chop them into small chunks.
Cook sweet potatoes in boiling water with salt for 10 minutes. Check them to see if they are tender and then remove and drain.
Smash the potatoes, season them, and keep them warm while you make the rest of the meal.
Trim off the ends of the spring onions. Cut the chilies in half and deseed them. Place onions and chilies in the pan with the steak fat and cook until lightly brown.
Take all of the crispy fat and four of the onions out of the pan and set them aside. The remainder of the pan’s contents (onion, garlic, and chilies) can be placed into a blender. Don’t start the blender yet.
Add in the parsley, half a tablespoon of extra virgin olive oil, and half a tablespoon of red wine vinegar. Blend until they are smooth and season with salt and pepper to taste.
Remove the steak sinew and season your steak with sea salt and pepper. Place in a nonstick frying pan on high heat and cook until it is as done as you want, turning every minute as it cooks.
Rest the steak on top of the spring onion for a couple of minutes and then slice.
Dish out a little sauce onto your plate, along with the steak, sweet potato, crispy fat and onions. The unused sauce can be stored in the fridge for future use.