Preheat oven to 400 degrees F and line a baking sheet with parchment paper.
To the prepared baking sheet, add all the tomatoes, onions, garlic bulbs, thyme, basil stems, salt and pepper. Drizzle with olive oil and balsamic vinegar.
Roast in preheated oven for about 45 minutes, or until everything is completely softened.
In the meantime, prepare your grilled cheese croutons.
Slice bread and add both cheeses.
Heat on a non-stick pan over medium-low heat, add butter, and cook each side for 3-4 minutes.
Let rest for a minute and then cut into small squares.
Once roasted veggies are done, add to a blender until very smooth. **Optionally, you can use a strainer to filter the blended mixture when pouring into a pot.**
Pour strained veggies into a pot and add chicken broth, heavy cream, basil, cheese and garlic salt.
Heat for about 10 minutes on medium-low, stirring occasionally .
Serve in an oven safe bowl and top with grilled cheese croutons.
Optionally, add a bit of cheese on top of the bowl and broil in the oven for 1-2 minutes for an extra cheesy top. Enjoy!