Step by Step method

1. Step 1.

   Tear 1/2 slice bread into 1-inch pieces; set aside.

2. Step 2.

   Melt 1 tablespoon butter in medium saucepan over medium-low heat.

3. Step 3.

   Add onion, garlic, bay leaf, 1/4 teaspoon salt, and pepper flakes, if using. Cover and cook until onion is softened, 3 to 5 minutes, stirring occasionally.

4. Step 4.

   Add tomatoes and their juice, broth, sugar, and bread pieces to saucepan, breaking up tomatoes with wooden spoon. Cook, uncovered, until bread pieces break down, about 5 minutes, stirring occasionally.

5. Step 5.

   Remove from heat; discard bay leaf.

6. Step 6.

   Transfer soup to blender jar and process until smooth and creamy, about 2 minutes. Return soup to saucepan and season with salt and pepper to taste. (Alternatively, use an immersion blender directly in saucepan, blending until smooth, about 3 minutes, then season.)

7. Step 7.

   Using remaining 4 slices bread, make 2 sandwiches with 2 cheese slices each.

8. Step 8.

   Preheat 12-inch skillet over medium-low heat for 3 minutes.

9. Step 9.

   Brush 1 side of sandwiches with half of melted butter. Place sandwiches buttered side down in skillet. Brush tops of sandwiches with remaining melted butter.

10. Step 10.

    Cover and cook until sandwich bottoms are golden brown, 4 to 8 minutes, moving sandwiches as needed for even browning.

11. Step 11.

    Using metal spatula, flip sandwiches and continue to cook, covered, until golden brown on second side and cheese is melted, about 3 minutes.

12. Step 12.

    Bring soup to simmer over medium heat. Ladle into bowls, sprinkle with chives, and serve with sandwiches.