In a Dutch oven over medium-high heat, melt 3 tablespoons of unsalted butter until bubbling. Add 1 diced onion and 1 cup of sliced celery, stirring until translucent and softened.

Stir in 2 minced garlic cloves and sauté for an additional 1-2 minutes until fragrant.

Sprinkle 2 tablespoons of flour over the sautéed vegetables and stir to coat, allowing to cook for about 1 minute.

Pour in one 28-ounce can of diced Marzano tomatoes along with 2 cups of chicken broth and bring to a vigorous boil.

Remove from heat and use an immersion blender to puree the mixture until smooth.

Reduce heat to low and cover the pot, allowing to simmer for 15 minutes, stirring occasionally.

Stir in 1 cup of heavy whipping cream and season with ¾ teaspoon of sugar, ¼ teaspoon of dried basil, and salt and pepper to taste.

Preheat your broiler, slice French or ciabatta bread, top with 1½ cups of shredded mozzarella cheese, and broil for 2-3 minutes until bubbly.

Ladle the hot tomato bisque into bowls and top with cheesy toasted bread or croutons.