2 tablespoons butter

2 tablespoons finely chopped onion

2 tablespoons finely chopped seeded fresh poblano pepper

2 tablespoons finely chopped seeded serrano pepper

1 garlic clove, minced

1 teaspoon finely chopped chipotle pepper in adobo sauce

2 teaspoons cornstarch

1 can (12 ounces) evaporated milk

2 cups shredded Monterey Jack cheese

1 cup shredded sharp white cheddar cheese

1 tablespoon chopped tomato

1/2 teaspoon ground cumin

1/4 teaspoon salt

1/4 teaspoon pepper

Tortilla chips