Rinse the parsley, cilantro (if using), and oregano under cold water. Shake off excess water and pat dry thoroughly with paper towels or a clean kitchen towel. Remove thick stems from the parsley and cilantro; use mostly leaves and tender stems. Finely mince the parsley, cilantro, and oregano by hand or pulse once or twice in a food processor — avoid over-processing into a puree. Finely mince the garlic.

Combine ingredients

In a medium bowl combine the minced parsley, cilantro, oregano and garlic. Add the red wine vinegar, lemon juice (if using), crushed red pepper flakes, kosher salt and black pepper. Stir to combine.

Emulsify with olive oil

Slowly drizzle the extra-virgin olive oil into the herb mixture while stirring constantly to help emulsify the sauce. Continue until the oil is fully incorporated and you have a loose, spoonable sauce. If you prefer a thinner chimichurri, add up to the extra 1 tablespoon of olive oil from the Finishing section.

Adjust seasoning and texture

Taste and adjust salt, pepper and acidity: add more salt if it tastes flat, more vinegar or a squeeze of lemon if it needs brightness, and a pinch more red pepper flakes if you want more heat. If the sauce is too coarse, pulse 1–2 short bursts in a food processor to reach the desired consistency; do not purée.

Rest to marry flavors

Cover the bowl and let the chimichurri rest at room temperature for at least 20–30 minutes to allow flavors to meld. For best flavor, refrigerate for 2–4 hours or overnight. If chilled, bring back to room temperature before serving (about 20–30 minutes) and stir again.

Finishing (optional)

Before serving, stir in the extra chopped parsley for a fresh look and, if needed, add the extra tablespoon of olive oil to loosen the sauce. Transfer chimichurri to a small bowl or jar and serve alongside grilled steak, chicken, fish, roasted vegetables, or as a condiment for sandwiches.