In a saucepan, melt the butter and whisk in the flour until there are no clumps. Heat over medium-low heat until the mixture is light caramel in color.

Add the milk in slowly and continue whisking until integrated and smooth. The mixture should be thick enough to coat the back of a spoon.

Add in the cheeses and melt in completely.

Add in the jalapeno juice, salt, and chili powder, and whisk in until completely integrated.

If the mixture is too thick, add in a little milk about a tablespoon at a time until ideal thickness is reached.

Remove from heat and serve warm with tortilla chips and desired fixings.