Chimichurri Sauce: 2 cloves garlic, peeled 1 jalapeño pepper, stemmed, halved, and seeded (or more, to taste) 3/4 c. packed stemmed parsley leaves 1/2 c. olive oil 2 Tbsp. red wine or sherry vinegar 1/4 tsp. salt 1 1/2 tsp. dried oregano leaves 1/2 tsp. dried red pepper flakes (optional)
Burgers: 1 1/2-lbs. ground beef chuck 1/2 tsp. salt 1/4 tsp. freshly ground pepper 4-oz. Gouda Cheese, diced 4 Kaiser rolls or hamburger buns, split
For the sauce, combine the garlic and jalapeño in a food processor. Process until finely minced. Add the parsley; process until finely minced. Scrape down the work bowl. Add the oil, vinegar, and salt; process until well-combined. Transfer to a small bowl. Stir in the oregano and red pepper flakes. Let the sauce rest for 2 hours, if possible, to blend the flavors.
For the burgers, prepare a barbecue grill or preheat a ridged grill pan. Spoon 3 tablespoons of the chimichurri sauce into a large bowl. Add the meat, salt, and pepper; mix well. Divide the mixture into 8 balls. Form each ball into a thin patty, about 5 inches in diameter. Divide the cheese over four of the patties, and top with the remaining patties. Seal the edges well, enclosing the cheese. Grill the patties over medium-hot coals (or follow ground meat directions if using a gas grill) or in the preheated grill pan for 5 minutes per side or until the internal temperature of the meat reaches 160° F. If desired, place the buns, cut sides down, on the grill during the last 1 minute of cooking, or toast the buns in the oven or under the broiler. Place the patties in the buns and serve with the remaining chimichurri sauce.
Note: If desired, additional Gouda cheese, thinly sliced, may be placed over the patties during the last minute of cooking.