Place the cubed bacon in a medium cast-iron pan over medium heat and stir until it turns crispy. Take out and set aside the bacon; throw away the bacon fat.
Using the same pan over medium heat, add the flour and unsalted butter. Whisk together. After the butter has fully melted, keep stirring often for 3 minutes to develop the roux. See chef’s note below about the roux.
Pour in the beer, stir, and allow to simmer for 2 minutes, stirring frequently. Adjust the heat as necessary to keep a simmer. After 2 minutes, pour in the milk and let it simmer for another 2 minutes.
Add the cream cheese and shredded cheeses, turn the heat down to low, and stir. The cheese will melt and blend after 2 minutes.
Stir in the remaining ingredients: Dijon, Worcestershire, and chives, and mix again.
Scatter the reserved bacon on top and serve right away, or move to a fondue or warming pot to keep hot and melted. Dip with fresh pretzels, corn chips, and grilled sausage.