Preheat the oven to 375°F.
Arrange the tomato halves on a baking sheet. Drizzle with olive oil and sprinkle with salt and black pepper.
Roast the tomatoes for 1 hour. Remove from the oven and set aside.
Heat 2 tablespoons of olive oil or butter in a large pot or Dutch oven over medium-high heat.
Add the diced onion and sauté for about 5 minutes until softened.
Stir in the minced garlic, thyme, salt, and pepper. Cook for another minute.
Add the crushed tomatoes, chopped basil, and sugar to the pot. Reduce the heat and simmer for 10 minutes.
Pour in the chicken stock and add the roasted tomatoes. Simmer for 30 minutes, stirring occasionally.
Use an immersion blender to puree the soup, or carefully transfer it in batches to a blender or food processor. Return the pureed soup to the pot.
Stir in the heavy cream.
To make the mini croutons: cut a few small pieces of bread into cubes, toss with a little olive oil, minced garlic, and chopped basil. Bake at 400°F for about 7 minutes until crispy.
Serve the soup topped with the croutons immediately.