Preheat the oven to 200°C. Line a baking tray with parchment paper.
Spread the tomatoes and garlic cloves over the tray. Drizzle with 60 ml olive oil, season with salt and pepper and toss to coat. Roast for 1 hour, until very soft and caramelised around the edges.
About 30 minutes before the tomatoes are ready, heat 1 tbsp olive oil in a large pot. Cook the onion for 6–7 minutes until soft. Add the dried basil and oregano and cook for another 1–2 minutes.
Add the balsamic vinegar and cook until reduced by half. Add the vegetable broth and thyme, bring to a boil and simmer for 10–15 minutes.
Remove the thyme. Add the roasted tomatoes to the pot. Squeeze the roasted garlic from the skins and add it too.
Add the cream, if using, and fresh basil. Blend with an immersion blender until smooth. Add a little extra broth if needed.