In a large pot, heat olive oil over medium heat. Toss in the diced onion and cook until translucent (about 5 minutes). Add the garlic and cook for another minute until fragrant.

Pour in the crushed tomatoes and vegetable broth. Bring the mixture to a gentle simmer and let it bubble away for about 10 minutes.

Using an immersion blender, carefully blend the soup until creamy and smooth. If using a regular blender, do so in batches while being cautious with hot soup.

Stir in the heavy cream and sugar. Season generously with salt and pepper. Let it simmer for another 5 minutes to combine the flavors.

Spread butter on one side of each bread slice and place them in a hot skillet. Layer cheese between two slices and toast until golden brown, flipping once.

Once golden and gooey, remove the sandwiches from the skillet and cut them into bite-sized croutons.