Heat a large skillet over medium heat, add in the chopped bacon and cook, stirring frequently, just until the bacon's crisped. Transfer the cooked bacon to a paper towel lined plate to drain the excess grease and cool completely.

Heat a second large skillet over medium heat, adding the butter and melting it. As soon as the butter's melted, add in the onions and cook just until they're soft and becoming transparent. Stir in both mustards and slowly pour in the beer, scraping the bottom of the pan as you stir. Bring the mixture to a boil and let it boil vigorously for about 5 minutes, stirring occasionally.

Lower the heat to medium, and stir in the cream cheese until the mixture's smooth and creamy. Turn off the heat, but leave the skillet on the burner.

Stir in the cheddar cheese, except for 1/4 cup to be reserved, about a cup at a time, until the mixture's again smooth, creamy, and thick. Stir in 3/4 of the bacon, saving the rest for the top of the dip.

Scoop the dip into an oven safe serving dish and sprinkle the remaining cheese and bacon out evenly over top.

Bake the dip at 350 degrees for 20-25 minutes, or until the dip is heated through and the cheese is bubbly.

Remove the dish from the oven and allow it to cool slightly. Serve the dip warm with chips, pretzels, crackers, or crusty bread.