In a large food safe bowl, add all the ingredients for the steak marinade and mix thoroughly. Add your steak into the marinade, mix, cover and place in the fridge for at least 4 hours but ideally overnight.
Preheat your grill using Cowboy Charcoal to medium-high temperature about 350F.
Add a skillet to the grill. Add your butter and flour to the skillet to melt and mix for 1-2 minutes. Once thickened into a paste, slowly add half of your milk and let the mixture thicken. Finally, add your shredded cheese and keep stirring until fully integrated and smooth. Once smooth, add the hatch chiles and the rest of the milk. When the sauce is done (about 10 minutes), pull it off and keep warm.
Add more Cowboy Charcoal until high heat (about 400F). Next, add the steaks to the grill and cook for about 3-4 minutes per side until medium rare (about 120 internal). When the steaks are done, pull off and let rest for 10 minutes.
Slice up your steak into cubes and begin building your nachos. Start with a layer of tortilla chips, shredded cheese, chopped steak, sliced jalapenos and diced red onions. Drizzle your queso over everything and top with sour cream, guacamole and chopped cilantro. Serve and enjoy!