In a large skillet over medium heat, combine the bourbon whiskey, garlic, and onion. Simmer until the onion becomes translucent, about 10 minutes, allowing the whiskey to reduce slightly.

Reduce heat to low and add the ketchup, apple cider vinegar, and Worcestershire sauce. Stir until well combined.

Add the brown sugar, molasses, liquid smoke (if using), smoked paprika, black pepper, cayenne pepper, and salt. Stir thoroughly to combine all ingredients.

Bring the mixture to a gentle simmer, then reduce heat to low. Allow to cook uncovered for 20-25 minutes, stirring occasionally to prevent sticking.

As the sauce simmers, it will thicken and the flavors will intensify. If it becomes too thick, add a splash of water or additional whiskey.

Remove from heat and allow to cool slightly before transferring to glass containers or jars for storage.