To make the chimichurri you need to first cut the root and stems off the cilantro and wash it thoroughly to ensure that it is clean and all dirt has been washed off. Next seed the serrano peppers (you may want to use gloves so you do not get pepper juice on your hands). Place cilantro, peppers, lime juice and oil in a food processor. Blend it unitl it is a nice consistency for a sauce. Place in the fridge.
Let the steak get to room temperature. sprinkle with coarse salt and cracked pepper. Grill the steak to your preference. Serve with chimichurri.