Grate your cheeses, and mix them together with the corn starch. If you use a pre-grated cheese, reduce cornstarch fractionally. Most pre-grated cheeses have some cornstarch on them already to keep the shreds from clumping.
Put cheese and cornstarch mix, evaporated milk, chopped jalapeno, chipotle in a pot, and heat over medium heat. Use a whisk, and stir/whisk, while heating the cheese mixture, it will slowly get lose, and stop clumping, and eventually, it will be pourable. It takes about 10 minutes of stir time.
Taste, add salt, and adjust to your preference, adding more chipotle if you want a stronger flavor.
Remove from heat, and pour into a bowl for dipping!
Notes
A thin skin will set up on top of the cheese, just stir it occasionally. If making ahead of time, just reheat before serving.