Place all sauce ingredients in a food processor and process just until incorporated and slightly chunky. Salt and pepper to taste.
Place steak on a sheet pan, salt and pepper, spread crushed garlic and drizzle with olive oil. Let steak rest for 30 minutes to 1 hour before grilling. Preheat grill or grill pan on high heat. It’s very important to have a hot grill because the skirt steak needs a good sear, 4-7 minutes per side. Let the steak rest 6-8 minute before slicing. Slice the meat against the grain into 1/4 inch strips. While meat is resting grill flatbread over medium heat.
Place the skirt steak strips over flatbreads with a dollop of Greek yogurt, chimichurri sauce and fresh cilantro. Serves 4.