Chipotle Queso Blanco

2 tablespoons unsalted butter
3 tablespoons finely chopped yellow onion
3 tablespoons finely chopped poblano pepper
2 tablespoons finely chopped serrano pepper
1/4 teaspoon salt
1 teaspoon minced garlic
1 tablespoon diced tomato
1/2 teaspoon ground cumin
1/4 teaspoon ground chipotle
1 cup heavy cream
1 tablespoon cornstarch
8 ounces shredded sharp white cheddar cheese
8 ounces shredded Monterey Jack cheese
1/4 cup sour cream

Melt the butter in a medium saucepan over medium heat. Add the onion, poblano pepper, serrano pepper, and salt. Cook until softened, about 2 to 3 minutes.
Add the garlic, tomato, cumin, and ground chipotle. Cook for about 1 minute, until the garlic becomes fragrant.
Add the heavy cream and bring to a simmer over medium heat, stirring constantly. Reduce the heat to low and simmer.
Sprinkle the cornstarch over the shredded cheddar and Monterey Jack cheeses. Toss to coat.
Add the cheese to the saucepan in batches—add a third of the cheese, stir until the cheese has melted, and add the next portion of cheese. When all the cheese has melted, add the sour cream. Serve with tortilla chips or your favorite dippers.