01 - Preheat oven to 400°F. Slice the top off the head of garlic, drizzle with 1 teaspoon olive oil, wrap in foil, and place on a baking tray alongside quartered tomatoes. Drizzle tomatoes with 1 tablespoon olive oil and sprinkle with salt and pepper. Roast for 35 to 40 minutes until tomatoes are soft and garlic is caramelized.
02 - While vegetables roast, heat 1 tablespoon olive oil in a large pot over medium heat. Sauté chopped onion for 5 to 7 minutes until translucent.
03 - Toss bread cubes with olive oil, dried Italian herbs (if using), and salt. Spread on a baking sheet and bake for 10 to 12 minutes, tossing once, until golden and crisp. Set aside.
04 - When roasted, squeeze garlic cloves out of skins. Add roasted tomatoes with their juices and garlic to the pot with onions. Stir in vegetable broth and bring to a simmer for 10 minutes.
05 - Stir in fresh basil leaves and sugar if using. Remove from heat.
06 - Use an immersion blender or transfer in batches to a blender to puree soup until smooth. For a silkier texture, strain through a fine mesh sieve.
07 - Stir in heavy cream or coconut milk if desired. Adjust seasoning with additional salt and pepper to taste.
08 - Ladle soup into bowls, top with croutons and extra fresh basil leaves.