Add jalapeño, red chili pepper, evaporated milk, salt, chili powder, and black pepper to a saucepan. Bring to a boil over medium-high heat.
Add both shredded cheeses and stir until cheese has melted.
Serve warm.Cornstarch is completely optional if you feel that your queso dip needs to be thicker. Simply sprinkle over sauce and whisk in over medium heat.
Notes
We're using a combination of white cheddar and mozzarella cheese for this white cheese dip. I highly suggest shredding the cheese yourself straight from the block. Bagged shredded cheeses contain an anti-caking agent that can cause the melted cheese to taste gritty. You can use white American cheese in place of the white cheddar if desired.
Both jalapeno and red chili pepper add a nice kick of spice. You can also use green chiles, chipotle peppers, or poblano.
Store the dip in an air-tight container kept in the refrigerator for up to 3 days. Leftovers should be tossed if they sit at room temperature for longer than two hours. Reheat leftovers in the microwave or in a saucepan over medium-low heat until warmed through.