In a large saucepan, melt the butter over medium heat. When it just begins to bubble, add in the flour to make a roux. Stir to combine the ingredients and cook the roux over medium heat for about 1 minute.
Whisk in the 2 tablespoons of milk. Pour in the the pilsner, and stir to combine the ingredients.
Stir the mixture over medium heat until it just begins to simmer and has thickened. Remove the pan from the heat.
Add in the Cheddar and Jack cheeses. Stir until the cheeses have melted and the mixture is smooth.
Add in the chiles, salt, onion powder and Worcestershire sauce and whisk them in completely.
Pour the cheese dip into a heatproof serving dish.
Garnish with chopped scallions and a sprinkle of cayenne. Serve the cheese dip while warm, with tortilla chips, pita chips or toast points.