To make a good chimichurri sauce by Mark Bittman, mix 2 cups of chopped parsley with 2/3 cup of olive oil, 6 tablespoons of lemon juice, 2 tablespoons of minced garlic and 2 teaspoons of crushed red pepper in a bowl. Season the mixture with salt and pepper to taste.
Alternatively, make a more complex-flavored chimichurri by combining 1/2 cup of red wine vinegar with 1 teaspoon of kosher salt, four cloves of minced garlic, one finely chopped shallot and one finely chopped red jalapeño. Stir 1/4 cup of minced flat-leaf parsley, 1/2 cup minced cilantro and 2 tablespoons of chopped fresh oregano into the bowl. Whisk 3/4 cup of olive oil into the mixture, and season it to taste with salt and pepper.
Reserve 1/2 cup of the sauce to use as a sauce. Use the remainder of the sauce to marinate meat in the refrigerator for three hours or longer. Before cooking it, remove the meat from the chimichurri marinade, pat it dry, and cook it as desired. Serve the meat with reserved chimichurri sauce spooned over the top.
Another option is to make a smoother chimichurri sauce by processing the parsley, red wine vinegar, garlic, fresh oregano and crushed red pepper flakes until it's smooth. Season it with salt and pepper before transferring the sauce to a serving bowl, and pouring 1/2 cup of olive oil over the top. Allow the sauce to stand for a minimum of 20 minutes.