Pesto:
2 garlic cloves, peeled
2 garlic cloves, peeled
1/4 teaspoon kosher salt
1/4 teaspoon dried hot red pepper flakes
1 1/2 cups (lightly packed; about 1 1/2 ounces) fresh basil leaves
1/4 cup pine nuts, toasted
1/3 cup (about 2 ounces) freshly grated Parmesan cheese
1/4 cup extra-virgin olive oil
1 1/2 pounds ripe heirloom tomatoes, cut into 3/4- to 1-inch pieces
1 tablespoon balsamic vinegar
Salt and freshly ground black pepper
1 loaf ciabatta
1 8-ounce piece Gruyère cheese, rind trimmed, cheese grated (about 2 lightly packed cups)
1 4-ounce wedge brie cheese (such as St. Andre), sliced
Using a Bump and Grind or another large mortar and pestle, mash (“bump”) garlic, salt, and pepper flakes into a coarse puree. Add 1 cup of the basil and pound (“bump”) until it is coarsely chopped. Add the remaining 1/2 cup of basil and pound until the basil forms a coarse puree. Add the pine nuts and pound just to break them up. Add the cheese and oil and mash until the nuts are coarsely ground and the mixture is well blended. Makes about 1 cup.
Prepare the barbecue for high heat (500°F).
Toss the tomatoes with the vinegar and season with salt and pepper. Set aside and toss occasionally.
Using a large serrated knife, cut the ciabatta horizontally in half. Spread both cut sides with pesto then top each with Gruyère cheese then brie cheese.
For a 2-burner gas grill, turn 1 burner off and place the ciabatta halves, cheese side up, on the grill rack over the unlit burner. For a 3-burner gas grill, turn the left and right burners off, leaving the center burner on. Place the ciabatta halves on the grill rack over the unlit burners. For a charcoal grill, pile the charcoal on 1 side of the barbecue and place the ciabatta halves atop the grill rack on the opposite side. Placing the ciabatta over the unlit burners ensures it doesn’t char too much.
Close the barbecue hood and grill until the cheese melts and the bread is golden brown, about 10 minutes. Avoid opening the hood too often in order to maintain the heat inside the barbecue.
Transfer the sandwich to a cutting board. Scatter the tomatoes over the bottom half of the ciabatta; discard the juices in the bowl. Cover with the top half of the ciabatta, cheese side down, and press gently. Using a serrated knife, cut the sandwich into 6 pieces and serve.