In a large non-stick skillet, combine the butter and olive oil over medium-hight heat. Once the butter has melted, whisk in the brown sugar and 1 teaspoon of salt. Add the onions, and saute on medium-high heat for about 5 minutes, stirring constantly. Lower the heat to medium-low and caramelized the onions for approximately 40-45 minutes.
Once the onions have just begun to brown, add the IPA beer and crank the heat back up to medium. Cook until the beer has cooked out and reduced and all you have left are the caramelized onions. This will take 5-10 minutes. Remove from heat and set aside to cool slightly.
Preheat your oven to 400 degrees F.
In a medium bowl, stir together the mayo, cream cheese, sour cream, bacon, a dash of salt and pepper and most of the cheese (reserving about 1 ounce to sprinkle on top). Add the caramelized onions to the mixture and stir to combine.
Pour the mixture into an 8x8 inch baking dish, and smooth to even out. Sprinkle the remaining cheese on top and bake, uncovered, for about 20-25 minutes, or until the top is bubbly and just beginning to brown.
Remove from heat and serve immediately with crusty bread or tortilla chips. Enjoy!