Roughly chop the green pepper, shallot, and garlic.
Place the green pepper, shallot, garlic, oregano, basil, parsley, coriander, chili flakes, olive oil, pepper, and salt in a blender or food processor.
Blend briefly until you have a coarse chimichurri. The sauce should still have some texture.
Pat the sirloin dry and season with salt and pepper.
Optionally, mix the sirloin with half of the chimichurri several hours or a night in advance
to give the meat extra flavour.
Save the other half of the chimichurri for garnish.
Sear or grill the sirloin on the barbecue or in a hot grill pan to your desired doneness. For a beautiful rare steak, sear the meat briefly but intensely so that it is nicely caramelised on the outside.
Let the meat rest for 5 to 10 minutes under loose aluminum foil so that the meat juices redistribute.
Just before serving, pour about half of the remaining chimichurri into the bag of crisps.
Close the bag and shake well so that all the crisps are covered with the herby sauce.
Spread the chimichurri crisps over a large dish.
Slice the sirloin into thin strips and arrange over the crisps.
Spoon the rest of the chimichurri over the meat.
Garnish with extra flat-leaf parsley, the zest of the limes, and a few drops of fresh lime juice.
Serve immediately so that the crisps remain deliciously crispy.