16 slices sourdough bread
8 tablespoons (1 stick) butter, at room temperature
One 5.2-ounce container of soft, spreadable cheese
8 ounces fresh mozzarella cheese, sliced into 8 thick pieces
Tomato Soup:
One 14-ounce can tomato sauce
⅓ cup tomato paste
½ cup heavy cream
1 teaspoon dried thyme
2 eggs
Salt and freshly ground black pepper
To Finish:
½ cup shredded white cheddar cheese
Preheat the oven to 350°F. Grease a 9-by-13-inch casserole dish with nonstick cooking spray. Make the sandwiches: Butter one side of each slice of bread with ½ tablespoon soft butter. Flips the slices over and spread 1 tablespoon Boursin on 8 pieces of the bread. Place 1 slice of mozzarella on top of the Boursin and then finish with one more piece of bread, butter side up, to close the sandwiches. Heat a griddle or large skillet over medium-high heat. Working in batches, place the sandwiches on the hot griddle and cook until both sides are toasted, 2 to 3 minutes per side. Set the sandwiches aside. Make the soup: In a medium pot, whisk the tomato sauce with the tomato paste until smooth. Heat over medium-low heat until it begins to simmer. Stir in the cream and thyme. In a medium bowl, whisk the eggs. Pour about a third of the hot tomato mixture into the eggs, whisking constantly to combine. Return the mixture to the pot and heat over low heat, stirring constantly, until the mixture thickens slightly, 3 to 4 minutes. Season with salt and pepper. Make the casserole: Pour half of the tomato mixture into the prepared casserole dish. Arrange the sandwiches inside the dish and then pour the remaining tomato mixture on top. Sprinkle the cheddar evenly over the casserole. Bake until the tomato mixture is bubbly and the cheese is melted, 25 to 30 minutes. Let cool for 5 minutes before serving warm.