Brown the chorizo: In a medium skillet over medium heat, cook the chorizo, breaking it into small crumbles, until browned and cooked through, about 6–8 minutes. Drain excess fat, leaving about 1 teaspoon in the pan. Transfer chorizo to a plate.

Sauté aromatics: In the same pan, melt the butter. Add onion and jalapeño; cook until soft and fragrant, 3–4 minutes. Stir in garlic, cumin, and chili powder; cook 30 seconds.

Warm the milk: Pour in evaporated milk and bring to a gentle simmer over medium-low heat. Stir often to prevent scorching.

Thicken lightly: Whisk in the cornstarch slurry. Simmer 30–60 seconds until slightly thickened. Don’t let it boil hard—gentle heat keeps the cheese smooth.

Add the cheeses: Lower the heat to low. Add the white American cheese in small handfuls, stirring until melted before adding more. Follow with the Oaxaca or Monterey Jack, stirring until completely smooth.

Season and finish: Stir in lime juice and half of the cooked chorizo. Taste and season with salt and pepper. If it’s too thick, add a splash more milk; if too thin, let it simmer a minute.

Serve: Transfer to a warm serving bowl. Top with the remaining chorizo and a sprinkle of cilantro. Serve immediately with tortilla chips.