In a large saucepan over medium-high heat, warm the oil. Add the onion and cook until it is tender but not browned, 5 to 7 minutes, stirring occasionally. Add the garlic and cook until fragrant, about 1 minute, stirring constantly to prevent browning. Remove the pan from the heat and slowly pour in the whiskey (beware of any flames). Return the pan to the heat and cook until the whiskey has almost completely evaporated, about 2 minutes. Stir in the tomato paste until well incorporated. Add the syrup, vinegar, mustard, paprika, hot pepper sauce, and pepper and simmer for 2 to 3 minutes to meld the flavors and thicken the sauce slightly. Remove from the heat and set aside.
Lightly brush the steaks on both sides with oil and season evenly with salt and pepper. Allow the steaks to stand at room temperature for 15 to 30 minutes before grilling.
Prepare the grill for direct cooking over high heat (450° to 550°F).
Brush the cooking grates clean. Grill the steaks over direct high heat, with the lid closed as much as possible, until cooked to your desired doneness, 8 to 10 minutes for medium rare, turning once or twice (if flare-ups occur, move the steaks temporarily over indirect heat). Remove from the grill and let rest for 3 to 5 minutes. Serve warm with the sauce.