Start off by roasting the bone marrow over direct heat, this should only take about 8-10 minutes. A good way to know is by checking the inside, it will bubble. Wrap in foil and save.
Apply olive oil on the steaks and season them with your favorite steak rub, let them sit while you make the caramelized onions.
Place a cast iron skillet over low heat and add olive oil and butter. Once it's melted together add the onions with a pinch of salt. Stir every few minutes and repeat this for about 40 minutes, the onions will begin to turn a deep rich brown. At this point, add the Worcestershire sauce, balsamic glaze and bourbon. Let it cook slowly for another 10-15 minutes and stir every minute or two. Remove and place in a bowl.
In a food processor add a block of butter, unsalted, the caramelized onions, roasted bone marrow, garlic paste, red pepper flakes and white wine vinegar. Run the processor for a minute, or until it’s consistently blended and wrapped in saran wrap. Place it in the fridge for 45 minutes.
Add the steaks over direct heat for searing, 60-90 seconds per side, and then transfer them to the indirect side. When the steaks reach 118 degrees F internally add a tablespoon of the Caramelized Onion Butter. Let the steaks finish and remove.
Let the steaks rest for 8-10 minutes and then slice. Serve with your favorite sides and enjoy!
