In a medium saucepan over medium heat, melt the butter. Add the finely diced onion and cook, stirring occasionally, until softened and translucent, about 4–5 minutes. Add the minced garlic and chopped serrano/jalapeño and cook for another 30–45 seconds until fragrant.

Make a roux

Sprinkle the all-purpose flour over the softened aromatics and stir constantly for 1 minute to cook out the raw flour taste.

Add liquids

Slowly whisk in the whole milk until smooth. Then whisk in the chicken or vegetable broth. Bring the mixture to a gentle simmer, stirring frequently, for 2–3 minutes until it begins to thicken slightly.

Incorporate cream cheese

Reduce heat to low and add the softened cream cheese cubes. Stir until the cream cheese melts completely and the mixture is smooth, about 1–2 minutes.

Melt cheeses

Gradually add the shredded white American and Monterey Jack cheeses in small handfuls, stirring constantly and allowing each addition to melt before adding more. Maintain low heat to prevent the cheese from seizing or becoming grainy.

Season

Stir in the ground cumin, salt, and black pepper. Taste and adjust seasoning as needed. If the queso is too thick, thin with up to 2 tablespoons of additional milk or broth until desired consistency is reached.

Finish

Remove from heat and stir in the chopped cilantro and lime juice. Transfer the queso to a serving ramekin or bowl. Top with pickled jalapeños if using.

Serve

Keep the queso warm for service. If making ahead, rewarm gently over low heat or in a double boiler, stirring frequently to restore a smooth consistency. Serve as a side with chips, tacos, or burritos.