Prep the herbs. Wash and dry the parsley and cilantro very well.
Strip the leaves and tender stems. Finely chop by hand until you have about 1 packed cup of parsley and 1/2 cup of cilantro.
Mince the aromatics. Finely mince the garlic. If using a shallot or green onion, mince that too.
Aim for tiny pieces so they blend smoothly into the sauce.
Build the base. In a bowl, combine the parsley, cilantro, garlic, and optional shallot. Add 1 teaspoon dried oregano, 1/2 teaspoon red pepper flakes, 1/2 teaspoon black pepper, and 1 teaspoon kosher salt to start.
Add acidity. Stir in 2 tablespoons red wine vinegar and 1 tablespoon fresh lemon juice. Add a small pinch of lemon zest for a bright lift.
Stream in the oil. Pour in 1/2 cup extra-virgin olive oil while stirring to emulsify slightly.
The mixture should look loose and glossy, not pasty.
Taste and adjust. Add more salt, pepper, acid, or chili to taste. You’re aiming for a lively, balanced flavor where herbs and tang lead, and garlic and heat follow.
Let it rest. Cover and let the chimichurri sit for at least 15–30 minutes at room temperature so the flavors meld. Stir before serving.
Serve generously. Spoon over grilled steak, chicken, fish, roasted potatoes, charred vegetables, or use as a marinade.