3 garlic cloves, peeled 1 1/2 teaspoons kosher salt 1 cup parsley leaves and stems 1/2 cup fresh oregano leaves 1/2 teaspoon red-pepper flakes 1/2 teaspoon black pepper 3 tablespoons red-wine vinegar 1/2 cup extra-virgin olive oil 1 1/2 to 2 pounds boneless, skinless chicken thighs or breasts 1 tablespoon olive oil

1. Make the sauce: On a cutting board, smash and coarsely chop the garlic with 1/2 teaspoon salt. Mash the mixture using the side of your knife until a coarse paste forms. Move the paste to the side of the cutting board, then chop the parsley and oregano together with the remaining 1 teaspoon salt. Combine the garlic paste and the chopped herbs and chop and mash until the herbs are bruised and fragrant.
2. Transfer to a medium bowl. Add the red-pepper flakes, black pepper, vinegar and extra-virgin olive oil; stir to combine. (You should have about 3/4 cup chimichurri. It can be prepared in advance and refrigerated in an airtight container up to 2 days.)
3. Make the chicken: Pat the chicken dry. If thickness varies greatly, pound to an even thickness, about 1/2-inch. Rub half the chimichurri all over the chicken and let sit for at least 10 minutes. (You could also refrigerate overnight; just let it come to room temperature before cooking.)
4. Heat the olive oil in a large skillet over medium-high. Wipe off excess marinade from the chicken and cook until juices run clear, about 5 minutes per side for thighs and 4 minutes per side for breasts. (For grilling and oven instructions, see Tips below.)
5. Serve with remaining chimichurri spooned over top.