In a medium saucepan over medium-low heat, whisk together evaporated milk, corn starch, onion powder, garlic powder, and salt until combined. Start with half the salt amount if you'd like, adding the rest to taste.
Bring just to a light simmer (don’t boil!) for 1-2 minutes while frequently stirring. Keep stirring to ensure the cheese melts smoothly and the dip remains a consistent temperature.
Reduce heat to low and stir in the shredded cheese in batches, allowing each addition to melt completely. Taste test, adding additional salt as needed. If adding diced chiles or tomatoes, you can stir them in now, or transfer the dip to a serving dish and garnish as desired. Enjoy with tortilla chips.
