Add the cilantro, parsley, oregano, shallot, minced garlic, and jalapeño to a food processor. Pulse a few times until everything is roughly chopped.

Pour in the olive oil, lemon juice, and red wine vinegar. Add the kosher salt, smoked paprika, crushed red pepper flakes (if using), and black pepper. Pulse again until the mixture is well combined and finely chopped, but still has a little texture.

Place the chicken thighs in a large bowl or baking dish. Season lightly with salt and pepper, then spoon about ¼ cup of the chimichurri over the chicken. Toss until evenly coated. Cover and refrigerate for at least 20 minutes, or up to 24 hours for deeper flavor.

Remove the chicken from the refrigerator and let it sit at room temperature while you preheat your grill to medium-high heat.

Grill the chicken for about 5–6 minutes per side, or until fully cooked and the internal temperature reaches 165°F.

Let the chicken rest for a few minutes, then serve with the remaining chimichurri spooned over the top or on the side.