We like to serve this soup with (even more) Italian bread. Garnish with grated Parmesan cheese, if desired.
Adjust oven rack to middle position and heat oven to 425 degrees. Arrange bread in single layer on rimmed baking sheet and bake, stirring occasionally, until dry and lightly browned, about 10 minutes.
Meanwhile, heat oil in Dutch oven over medium-high heat until shimmering. Add chard stems, onion, carrots, and salt and cook until softened, about 7 minutes. Stir in garlic and pepper flakes and cook until fragrant, about 30 seconds. Stir in tomatoes and their juice and cook until slightly thickened, about 2 minutes. Stir in broth, beans, and chard leaves and bring to simmer. Reduce heat to medium-low; cover; and cook until vegetables are tender, about 10 minutes.
Stir bread into soup. Cover and cook until bread is softened, about 5 minutes. Off heat, whisk soup vigorously until bread is broken down, about 2 minutes. Season with salt and pepper flakes to taste. Drizzle individual portions with extra oil and serve.
