Substitute skirt steak with flank, ribeye or rump steak.
To make the marinade, mix together all the marinade ingredients in a bowl until well combined and pour into a zip lock bag.
Place the skirt steak into the zip lock bag with the marinade and turn to coat. Place in the refrigerator for 1 to 2 hours to marinate, the longer the better.
Slice the peppers and onions and grill the mixture in a large pan with a big glug of olive oil on a medium-high heat for about 10 minutes until the vegetables are a little charred and are starting to soften.
In the meantime, make the chimichurri sauce by adding all the sauce ingredients except the spring onions and blend in a food processor/blender until almost smooth (try to keep a bit of texture). Stir in the sliced spring onions andadjust the seasoning to taste.
Remove the beef from the marinade and season well with salt and freshly ground black pepper.
Cook the steak on a lightly oiled griddle pan over a high heat for 4 to 5 minutes on each side depending on the thickness of the meat. Medium-rare to medium is recommended. Transfer to a cutting board and allow it to rest.
To heat the tortillas place them directly on your stovetop, either using a gas burner on a low flame or an electric plate on a low heat (use a little non-stick spray for an electric plate). Warm each tortilla for about 30 seconds to 1 minute, flipping and repeating on the second side.
Once heated and slightly charred wrap the tortillas in a clean dishcloth to keep warm. Repeat until you have warmed all of your tortillas.
Thinly slice the steak against the grain on a diagonal.
To serve, generously spoon grilled peppers, tender steak slivers and chimichurri sauce onto warm tortillas and top with a few slices of avocado. To finish it off, sprinkle coriander leaves, red chillies and lime juice over the top and wrap up the tortilla.