To make the soup: Preheat oven 425 F. Place tomato halves on a parchment-lined baking sheet and drizzle them with the olive oil and a few pinches of salt. Transfer them to the oven to roast for 25 to 30 minutes.
In a pot, over medium-high heat, add 1 tablespoon olive oil. When the oil glistens, add the shallots. Cook the shallots until they’re soft and translucent, about 2 to 3 minutes. Next, roasted tomatoes, garlic, 2 pinches of crushed red pepper flakes, can of tomatoes, chicken stock and thyme leaves. Bring to a simmer, cook for 10 minutes. Using an immersion blender, pulse until smooth. (You can also transfer the soup, in batches, to a blender and pulse until smooth. Just be careful blending hot liquids, make sure you allow some steam to escape.) Salt to taste (I added about 1 to 2 teaspoons).
To make the basil oil: To a blender, add basil and olive oil. Blend until pureed. Pour the oil through sieve, discarding any of the basil bits. The oil should be bright and green. Set aside.
To make the grilled cheese croutons: Well, you know how to make a grilled cheese, but I’ll tell you anyway! Set a saute pan over medium-low heat. Melt 1 tablespoon of butter in the pan. Assemble the grilled cheese sandwiches. Add the sandwiches (you may need to cook them in batches or one by one) to the pan. Cook until golden brown on one side and then flip. Cover the pan with a lid to ensure maximum meltiness. Remove from the pan and set aside. Repeat with the remaining grilled cheese sandwiches. To make the croutons, cut them into squares.
To assemble: Divide the soup amongst bowls. Add a few croutons to the center of the bowl and drizzle with basil oil. Serve with the croutons on the side because one or two is not enough!