Slow-roasting tomatoes brings out all of their fantastic sweetness. Adding a dollop of mascarpone cheese makes them sing!

Preheat oven to 275 degrees F. Arrange tomato halves, cut side up, on a baking sheet. Scatter thyme sprigs and garlic on top of tomatoes. Season with salt and pepper and drizzle with 3 tablespoons olive oil. Roast until tomatoes have dried slightly and some of the skins have burst, about 2 hours. Meanwhile, in a small bowl, using a rubber spatula, stir together marscarpone and Parmigiano-Reggiano until smooth. Refrigerate. In a small stockpot over medium heat, warm 2 tablespoons olive oil. Add onion and saute, stirring occasionally, until tender and translucent. Add tomatoes, stock, and bread and simmer for 5 minutes. Put tomatoes and stock mixture in a food processor and puree. Salt and pepper to taste. Divide soup among 6 warmed bowls and top each with dollop of cheese mixture. Garnish with sprig of thyme through cheese.