Preheat your oven to 400°F. Spread the cherry tomatoes, chopped onion and peeled garlic cloves on a baking sheet in a single layer. Drizzle them with a little olive oil, sprinkle with a pinch of salt and pepper, and give everything a gentle toss. Pop into the oven for about 20-25 minutes, until they're beautifully roasted and bursting with flavor.
With an immersion blender or a regular blender blend the mixture until it's smooth.
Place the tomato. mixture in a large pot or a Dutch oven and pour chicken stock over.Allow the soup to simmer for about 10 minutes on medium-low heat, letting all the flavors meld together.
Toss in the chopped basil leaves, and let this simmer for another 5 minutes.
Pour in that half and half, and mix to combine everything.
Season it with additional salt and pepper if needed. Once you're satisfied, ladle the soup into bowls, garnish with a few fresh basil leaves, and parmesan cheese if desired Serve it up with crusty bread or your favorite crackers.