Melt the butter in a saucepan over medium heat and whisk in the flour, cooking for 1 minute, until it smells slightly toasted.

Slowly whisk in the stout, letting it bubble and thicken for about 1 minute.

Whisk in the milk and bring to a gentle simmer, stirring often, for 3 to 4 minutes, until the mixture coats the back of a spoon.

Reduce the heat to low and add the cheddar a handful at a time, stirring until each addition melts before adding the next.

Stir in the garlic powder, dry mustard, and salt, keeping the heat low, too much heat will cause the cheese sauce to separate.

Bake the pretzel bites according to the package directions while the sauce finishes.

Pour the warm beer cheese into a bowl and set it in the middle of a tray of warm pretzel bites for dipping.