Tip: Keep this cheesy dip warm in a slow cooker for maximum flavour and texture.
Set a large skillet over medium heat and add the butter. Once melted, add the onions and cook until starting to soften, 2 to 3 minutes. Add the green chiles and chipotle peppers and cook for a minute. Add the cheese and let it melt. Add the enchilada sauce and give it all a stir. Transfer to a slow cooker to keep warm.