* Butterfly chicken breasts: Put halves on a cutting board, smooth sides down, with the pointed ends facing you. Starting on one long side, cut breasts almost in half horizontally *(stop about 1/2 inch before reaching opposite side). Open cut breasts like a book. Sprinkle each piece all over with 1/8 teaspoon salt; season with pepper. Transfer to a plate, and coat both sides with garlic`and oil. For best results, let stand for 30 minutes (or prep in the morning and refrigerate to cook later). 

* Heat a grill or grill pan until medium-hot. Place 3 basil leaves on the bottom half of each opened chicken breast; top each with 2 slices tomato. Fold over other half of chicken breast, and secure with two toothpicks or short skewers.

* Grill chicken breasts, turning once, until golden brown on both sides and no longer pink in the center, about 15 minutes. Place on a clean serving platter, garnish with basil. If desired, remove toothpicks or skewers before serving.