Place the basil and garlic in the center of a large cutting board; sprinkle with the pine nuts and salt. Using a large, sharp knife, chop the basil with the rest of ingredients until the mixture is very finely chopped. Transfer the basil mixture to a bowl; stir in the olive oil to make pistou. (Pistou can be made up to 1 day ahead; cover and refrigerate.)
Spread the pistou over the cut sides of the bread. Cut each Burrata carefully into quarters or slice the mozzarella. Arrange the cheese atop the bottom halves of the ciabatta, dividing it evenly. Drizzle any remaining pistou over the cheese and season the cheese with salt and pepper. Top the cheese with tomato slices. Top the sandwiches with the top halves of the ciabatta and press gently to compress.
Wrap the sandwiches tightly with sandwich paper or plastic. (Sandwiches can be made up to 4 hours ahead. Keep at cool room temperature.)
Recipe excerpted with permission from <a href="https://www.amazon.com/gp/product/0847847470/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0847847470&linkCode=as2&tag=craftfocom-20&linkId=5a7b8c0cae6f92b46ccdd47286e489c4">The Portable Feast: Creative Meals for Work and Play</a> by Jeanne Kelley.