Preparation

Make the parmesan crackers:

Preheat the oven to 350°F. Arrange the cheese into 8 equal-sized piles on a parchment-lined baking sheet. Bake until the cheese spreads, and the crackers are lacy and golden, 10-11 minutes. Cool on parchment.

Make the soup:

Heat the oil over medium-high heat in a large saucepan. Add the onions and cook, stirring, until translucent, 6-7 minutes. Add the garlic and cook 1 additional minute. Add the tomatoes, broth, basil, salt, and pepper, bring to a boil, reduce heat and simmer until the soup has thickened slightly, 10-15 minutes. Remove from heat, cool slightly, and puree in a blender until smooth. Transfer to a lidded container, chill completely, season with additional salt and pepper to taste and stir in the cream, if desired. Divide the soup among bowls, swirl with the pesto and additional cream, if desired, and garnish with fresh basil. Serve with the lacy parmesan crackers.