Preheat oven to 375°F (190°C). In a medium bowl, toss the cubed day-old bread with 2 tbsp olive oil, 1 minced garlic clove, and a pinch of salt until evenly coated. Spread the bread cubes in a single layer on a baking sheet. Bake for 10-15 minutes, or until golden brown and crispy, flipping halfway through. Set aside.

Heat 2 tbsp olive oil in a large pot or Dutch oven over medium heat. Add the chopped yellow onion and cook until softened and translucent, about 5-7 minutes.

Add the minced garlic and cook for another minute until fragrant. Pour in the crushed tomatoes and vegetable broth. Stir well.

Bring the soup to a gentle simmer, then reduce heat to low, cover, and let it cook for at least 15-20 minutes, allowing the flavors to meld and deepen.

Remove the pot from the heat. Using an immersion blender, carefully blend the soup until smooth and creamy. Alternatively, transfer the soup in batches to a regular blender (be cautious with hot liquids, blending in small amounts and venting the lid), blend until smooth, and return to the pot.

Stir in the coconut milk (or heavy cream), chopped fresh basil, sugar, salt, and black pepper. Taste and adjust seasonings as needed. If desired, gently reheat for a few minutes without boiling.

Ladle the hot soup into bowls. Garnish generously with extra fresh basil and a handful of the homemade garlic croutons. Serve immediately alongside your favorite salad side dishes.