Heat a medium sized frying pan to a medium/high heat. Add the 3 tbsp of olive oil, 1/4 tsp of sea salt, and 1 tsp of course black pepper.
Rinse and slice the 3 cups of brussel sprouts in half, then add them to the frying pan. Brown each side of each brussel sprout and cook until tender and slightly crispy.
Add the 2 tbsp of aged balsamic vinegar and 1 tsp of black pepper into the same pan on a low heat and cook for 5 more minutes while stirring.