01 - Preheat the oven to 375°F. Toss bread cubes with olive oil, garlic powder, and salt. Spread evenly on a baking sheet and bake for 12 to 15 minutes, tossing halfway through, until golden and crisp.
02 - Heat 2 tablespoons olive oil in a large pot over medium heat. Add diced onion, carrot, and celery. Sauté for 6 to 8 minutes until softened.
03 - Add minced garlic to the pot and cook for 1 minute until fragrant.
04 - Stir in canned tomatoes with juices, fresh basil leaves, vegetable broth, sugar, salt, black pepper, and red pepper flakes if using. Bring to a gentle simmer.
05 - Reduce heat and simmer uncovered for 20 to 25 minutes, stirring occasionally, until the vegetables are very tender.
06 - Remove the soup from heat. Using an immersion blender or regular blender in batches, blend until completely smooth.
07 - Stir in heavy cream and gently reheat if necessary. Adjust seasoning to taste.
08 - Ladle the bisque into bowls and garnish with homemade croutons and additional basil leaves.