In a medium-sized saucepan, melt butter over medium heat.
Sauté the green onions and tomatoes until slightly softened, about 3 minutes. Add in the garlic and sauté for another 30 seconds.
Add the chiles and jalapenos and sauté for 1 minute.
Stir in the cumin, chili powder, and salt.
Pour in the evaporated milk and stir in the cornstarch. Cook over medium until it begins to bubble. Simmer for 1 minute until thickened.
Stir in the American cheese until melted and well combined.
Remove the pan from the heat and stir in the cheddar cheese until melted and well incorporated.
Keep over the lowest heat setting to keep the queso warm.
Cook The Beef
Heat the oil in a cast iron or heavy-bottomed pan over medium-high heat. Once the oil is hot, crumble the ground beef into the pan. Using a wooden spoon, break up any large chunks.
Cook the beef until it is cooked through, stirring only occasionally, about 8 to 10 minutes. The goal is to lightly fry the outside of the beef so it becomes a bit crispy, so only stir every couple of minutes or as needed.
Drain excess oil, if needed.
Remove the beef from the heat and stir in the salt and pepper.
Assemble the Nachos
On a large platter, lay out the tortilla chips in a single layer.
Ladle the queso over the chips.
Spoon the ground beef evenly over the chips.
Top with lettuce, tomatoes, red onion, and jalapenos.
Top the nachos with dollops of the sour cream or serve it on the side.
Serve immediately.
Notes
Be sure not to over stir the ground beef. You really want it to crisp up a bit.
I also highly recommend cooking the beef in a cast iron pan to achieve the perfect crispiness.