Preheat the oven to 325 deg F. Heat the olive oil in a wide braiser or Dutch oven over medium heat. Pat the short ribs dry and sprinkle generously with kosher salt. Place the short ribs in a single layer in the braiser.
Allow the short ribs to brown on the bottom before flipping over to another side. Continue cooking the short ribs until all sides are browned. Remove the short ribs to a plate and set aside.
Turn the heat down to medium low and spoon off all but 2 tablespoons of fat from the braiser. Add the finely chopped onion and sauté for 4 to 5 minutes until softened and golden brown. Add the minced garlic and sauté for another minute.
Carefully pour the bourbon into the braiser to deglaze the pan. Bring to a simmer, scraping the bottom of the pan to remove the browned bits. Add the balsamic vinegar, brown sugar, Worcestershire sauce, bay leaves, and 1 tsp kosher salt to the braiser. Add the beef broth and return the short ribs to the pan.
Cover with a lid and bake for 2 1/2 to 3 hours until the meat is extremely tender and falling off the bone. Check the short ribs every hour and spoon off as much of the fat as you can while basting them with the braising liquid.
Horseradish Sauce
In a small bowl, whisk together the sour cream, horseradish, Dijon mustard, lemon juice, salt, and pepper. Whisk in the heavy cream to thin out the sauce. Refrigerate until service.
To Serve
When the meat is tender, spoon off as much of the fat from the braising liquid as possible. The liquid will have reduced quite a bit and can be spooned over the short ribs. Serve with the horseradish cream sauce. Enjoy!