1 tablespoon unsalted butter
1 tablespoon all-purpose flour
1 1/4 cups real whole milk
1/2 teaspoon ground cumin
1/2 teaspoon granulated garlic
1/4 teaspoon kosher salt
1/4 teaspoon onion powder
Pinch ground black pepper
10 ounces (about 4 cups) shredded white American cheese
1 tablespoon diced canned green chiles or jalapeños (optional)
Fresh pico de gallo
Sliced jalapeño peppers
Make the roux: In a 3-quart saucepan (preferably one with sloping sides) melt the butter over medium-low heat. Once the butter is completely melted, sprinkle the flour over it and whisk the two together until a very loose paste forms. Cook the roux for 1 minute.
Make a béchamel sauce: Pour the milk into the roux in a slow, steady stream, whisking constantly. Adding the milk to the roux slowly helps avoid clumps.
Add the spices: Once all of the milk has been whisked into the pot, add the cumin, garlic, salt, onion powder, and black pepper. Whisk the spices in completely while bringing the milk up to a simmer.
Thicken the sauce: Whisk the milk sauce frequently until small bubbles appear on the surface. This should take 3-5 minutes. After 5 minutes, the milk sauce should thicken to the consistency of a bisque or soup.
Gradually whisk in the shredded cheese: Once the milk sauce has thickened, decrease the heat to the lowest setting. Whisk in the shredded cheese a heavy pinch at a time, adding the next batch of cheese only when the previous batch has melted completely.
Stir in the chiles: Once all of the cheese has been whisked in, add the diced green chiles to the queso blanco. Taste the sauce, adding more salt if needed.
Adjust the consistency: When first prepared, the sauce will be slightly thin. This is to allow the queso to thicken properly as it cools. If you find your queso is too thick, add more milk, a tablespoon at a time, until it reaches your desired consistency.
Keep warm over very low heat: If you plan to serve the queso blanco over the span of a couple of hours, keep the dip warm over very low heat. Stir every 10 minutes to keep it smooth. If the top of the dip starts to firm up, simply stir to replenish its creamy consistency.