Grilled Flank Steak with Chimichurri Sauce

For the chimichurri: Combine onion, garlic, parsley, thyme, oregano, chili flakes, and salt and pepper in a food processor bowl. Use pulse button to blend smooth. Add vinegar and then pulse again. Turn processor on continuous run and slowly drizzle in all oil until smooth. Transfer to a storage vessel and cover. Allow the mixture to rest for at least 2 hours before using.

Note: You can prepare chimichurri and refrigerate the day before using. If refrigerated, remove sauce from the refrigerator and bring to room temperature before using.

For the flank steak: Preheat gas grill to medium high. Preheat oven to 350°F. Pour olive oil over steak, smear with the garlic and mustard, and marinate for 1 hour. Remove meat from the marinade and season with salt and pepper. Sear meat on all sides over a hot open fire. Grill each side for 7 to 8 minutes. Place meat in oven and roast for 5 to 7 minutes or until medium rare (or until cooked to desired doneness). Remove from grill and transfer to a plate to let rest for 5 minutes before slicing. Use a sharp carving knife and slice meat on a bias. Transfer to plates and spoon sauce over top.