1. Preheat oven to 400 degrees. 2. Pat the steaks dry with paper towels and season generously with the salt and pepper. Heat the oil and butter in a large cast iron skillet over medium high heat. Cook the steaks 3 minutes per side (making sure to cook the sides). Transfer pan to the oven and cook an additional 2 minutes. Let steaks rest for 10 minutes. 3. Remove the skins from the jalapeno peppers, remove seeds and membranes. Place peppers in the bowl of the food processor with the oil, pepper, cilantro shallot, water and lime juice; process until smooth. 4. Place the mango, avocado, shallots, cilantro and mesclun greens in a large bowl. Add the dressing to the bowl and toss to coat. 5. Carve the steak into 1/2 inch thick slices. Mound the salad onto 4 serving plates. Fan the steak slices around the salad. Top with crumbled Cotija cheese.