11. Melt butter in a heavy-bottomed saucepan over medium heat until foaming subsides, about 2 minutes.
22. Whisk in flour, creating a smooth roux. Cook until mixture turns light golden and smells nutty, about 3-4 minutes.
33. Gradually pour in milk and cream, whisking constantly to prevent lumps. Simmer until mixture thickens and coats the back of a spoon, about 5-6 minutes.
44. Reduce heat to low. Add shredded cheeses in small handfuls, stirring continuously until completely melted and smooth.
55. Fold in green chiles, pickled jalapeños, cumin, garlic powder, and white pepper. Stir until fully incorporated.
66. Season with salt to taste. Keep warm over lowest heat setting, stirring occasionally.