Preheat a gas or charcoal grill to a medium-high temperature (about 400°F).
Place the ground beef in a shallow bowl. Add the panko crumbs (see notes below), salt and a few grinds of black pepper but don't mix yet.
Add the parsley, cilantro, 1 clove of garlic, 1 tablespoon of the olive oil and 1 teaspoon of the vinegar to the work bowl of a food processor. Add the oregano, hot sauce and a few grinds of black pepper and pulse the mixture until it's finely chopped.
Take a heaping tablespoon of this mixture and add it to the ground beef, then add the rest of the olive oil and vinegar to the processor along with the 1/4 teaspoon of salt. Pulse once or twice to combine, taste, adjust the seasonings and add more garlic if desired. Transfer the sauce to a small serving bowl and set aside.
Use a wooden spatula to combine the meat mixture as best you can before doing a final, gentle mix with your hands.
Gently form the meat into four patties and make a slight depression in the center of each with your thumb. This helps the burgers maintain an even thickness rather than developing a thicker "dome" in the center. Arrange the burgers on a plate, cover and refrigerate for at least 15 minutes before grilling.
Oil the grill grates and add the burgers. Grill until juices begin to bead on the top of each burger indicating that they are cooked through the center, approximately 4 minutes.
Turn the burgers carefully and grill for an additional 2 to 3 minutes on the second side. Transfer the burgers to a plate and allow them to rest for 5 minutes before serving.
To serve, place a slice of tomato on each bun, top with a burger and a small amount chimichurri sauce. Pass the extra sauce at the table.
Leftover chimichurri can be refrigerated for up to 2 days.
Tips for Making This Recipe
Add Panko Crumbs for Juicy Burgers
Our secret for tender, juicy grilled is to always add a small quantity of panko breadcrumbs (1 tablespoon per pound of ground meat) to our burgers. This helps to retain the natural meat juices in the burger during grilling.Adding the panko crumbs doesn't change the flavor or texture of the beef in the slightest. Unlike dry breadcrumbs, panko crumbs have a coarse texture that simply absorbs meat juices, without adding density to the texture of the burger. For most burger recipes, we also include a tablespoon of mayonnaise along with the panko for extra moisture, but the olive oil in the chimichurri sauce takes its place in this recipe.You can use this technique with just about any kind of ground meat. It's particularly good for turkey burgers where maintaining juiciness can be more of a problem.