Combine 3 cloves of finely minced garlic, 1/4 cup of balsamic vinegar, 1/4 cup of soy sauce, 2 tablespoons of Worcestershire sauce, 2 tablespoons of brown sugar, 1 tablespoon of Dijon mustard, 1 teaspoon of dried Italian herbs and 1/4 teaspoon of freshly cracked black pepper in a small bowl and set aside
Use the textured side of a meat tenderizer to lightly pound both sides of the London broil
Place the London broil in a gallon zip lock bag and add the marinade.
Seal the bag and chill for 8-12 hours flipping the bag at least twice
Transfer the bag out of the refrigerator 30 minutes before you want to cook the London broil
Add a few tablespoons of a neutral oil into a large skillet and place over medium to medium high heat
Remove the London broil from the marinade and dry both sides with paper towels (discard the marinade)
Once the skillet is very warm, carefully place the dried London broil into the skillet and cook undisturbed for 5-6 minutes or until the underside has developed a golden brown crust
Flip the London broil and cook on the other side for another 5-6 minutes or until the internal temperature reaches 130 degrees
Transfer the London broil onto a cutting board and cover with foil
Note: if your skillet is super hot, allow it to cool for a few minutes before making the pan sauce
Return the skillet to the stovetop, reduce the heat to medium and add a tablespoon of butter along with the minced garlic
Cook while stirring occasionally until the garlic softens and has become fragrant
Add 1 1/4 cups of beef broth and use a wooden spoon to work up any brown bits from the bottom of the skillet
Simmer the sauce for a few minutes and then whisk in a tablespoon of butter and the parsley and lemon juice
Transfer the skillet off of the heat
Slice the London broil thinly against the grain and top with the garlic pan sauce