To a small bowl, add garlic, soy sauce, olive oil, balsamic vinegar, paprika, salt, and pepper. Mix until combined.
To a zippered plastic bag, add the London broil and the marinade. Refrigerate for at least 2 hours, up to overnight.
When ready, take the London Broil out of the refrigerator about 30 minutes before you are ready to cook it to allow it to come to room temperature.
Preheat your oven to broil, positioning the rack in the middle of the oven.
Remove the London Broil from the marinade. Discard marinade.
To a large skillet over high heat, add the extra tablespoon of oil. When hot, sear the London Broil on both sides until browned, about 1-2 minutes per side.
Transfer the skillet to the middle rack in the preheated oven.
Broil for 10-12 minutes, flipping halfway, or until the internal temperature reaches 135°F (medium rare), or your desired doneness.
Remove the London Broil from the oven and let it rest for 10 minutes.
When ready to serve, slice against the grain into ¼-inch pieces and garnish with parsley.
Serve warm with chimichurri sauce.