In a medium saucepan over medium heat, melt the butter.
Whisk in the flour and cook for 1–2 minutes until it forms a smooth, bubbly paste (roux), but do not let it brown.
Gradually whisk in the milk, ensuring no lumps form.
Continue whisking until the mixture thickens and coats the back of a spoon, about 2–3 minutes.
Lower the heat to medium-low.
Add the shredded cheddar a handful at a time, stirring until melted and smooth.
Stir in the Laughing Cow cheese until fully incorporated and the sauce is creamy.
Stir in chili powder, pickled jalapeño juice and chopped pickled jalapeños.
Taste and add salt and black pepper as needed.
If the sauce is too thick, whisk in a splash more milk until desired consistency is reached