Prepare Spicy Mayo according to recipe below. Set aside or store in a tightly sealed container, in the refrigerator, until ready to serve.
Place ground beef or chuck in a medium mixing bowl.
Add salt and pepper and a few dashes of Tabasco sauce, to taste.
With your hands (wear kitchen gloves, if you like), mix the meat and seasoning well.
Form the prepared meat into 4 patties. Place on a plate and place plate into refrigerator until ready to use. Cover if it will be more than an hour.
Heat a medium skillet over low heat.
Add butter.
Add sliced onions and mushrooms.
Pour in bourbon. Stir to combine the ingredients. Allow to simmer for about 10 minutes, stirring occasionally.
When onions and mushrooms are tender, remove from heat and set aside.
Spread bottom and top of each Kaiser roll with about 1/2 tablespoon of butter.
Place them face down on a grill pan or skillet over medium heat. Lightly grill the rolls. Remove from heat and set aside to cool.
Form the prepared meat into 4 patties.
Place patties on a grill pan or skillet over medium to medium-low heat. Allow each to cook about 3 minutes, then, using a spatula, rotate 45 degrees, leaving it on the same side. Cook a bit more.
Flip the burger.
Add the cheese and cook it for a couple of minutes, rotating it 45 degrees again to get the nice grill marks. (You can easily skip all of this nonsense if you don't give a hoot about "perfect grill marks". We did.)
Spread spicy mayo on the tops and bottoms of the Kaiser rolls. Place both halves on serving plates.
Transfer the burger onto the bottom half of the bun.
Add a large helping of the prepared onion/mushroom mixture over top of the burger. Add an equally generous helping of crumbled blue cheese.
Top with 2 slices of bacon.
Place the top on the burger, if you like, or leave it open so your family and guests can admire this beautiful burger.
Serve hot.