1) To make the chimichurri, combine all your ingredients except the beef, cheese, and buns in a blender or food processor and whiz it up. If you don’t have a blender, you can very finely chop everything and stir it together with your vinegar and oil.
This will become stronger the longer it sits. It’s best in the one to two day range. After that it gets almost too strong.
2) If you’re grinding your meat yourself, cut it into chunks and pulse it a few times in the food processor, or you can get your butcher to grind it for you.
3) Form 6 ounce patties from the ground beef and put a big thumb depression in the center of each patty. Season well with salt and pepper.
4) I cook mine either in a grill over medium-high heat for 3-4 minutes per side or in a cast iron pan over high heat with just a drizzle of oil. Once the pan is very hot, add the burgers and make sure they don’t touch. Sear them on each site for about 4 minutes per side for medium rare.
5) If you’re using cheese, grate the cheese and add it to each burger a minute before they’re done. If you have a lid, cover the pan for the best melting.
6) Toast the bun and serve each burger with a lot of chimichurri sauce!