In a mixing bowl, whisk together olive oil, minced garlic, Dijon mustard, salt, and pepper until well combined. Place the flank steak in a resealable bag, pour in the marinade, and seal it tight. Let it marinate in the refrigerator for 1 to 4 hours, turning occasionally for even coverage.

While the steak marinates, preheat your grill to medium-high, aiming for about 400°F (204°C). Clean the grill grates with a brush and oil them lightly.

Remove the flank steak from the marinade and place it directly on the grill. Grill for 5-7 minutes on each side, until it reaches 130°F (54°C) for medium-rare.

Transfer the steak onto a cutting board and let it rest for about 5 minutes. After resting, slice the steak against the grain into thin strips.

In a mixing bowl, combine halved cherry tomatoes, bocconcini, and shredded fresh basil. Drizzle with a bit of olive oil and season with salt and pepper to taste.

Arrange the sliced flank steak on a large platter, spooning the Caprese mixture over the top. Drizzle balsamic glaze across the steak and toppings.