Season both sides of the London broil generously with salt and pepper.
Using the sear function on your slow cooker or a large skillet over medium-high heat.
Heat the slow cooker or the skillet and add in the butter and avocado oil.
Sear the London Broil for a few minutes on each side, or until each side is browned.
With the roast in the slow cooker, add in the onion and the garlic.
In a small bowl, mix together the beef broth, tomato paste, balsamic vinegar, brown sugar and Worcestershire. Pour the mixture over the roast.
Cook in the slow cooker on low for 8 hours, or high for 4 hours.
When finished, shred with two forks and serve with mashed potatoes or mashed cauliflower.
