Steeping chicken broth with sprigs of rosemary and thyme for just a few minutes adds great flavor to this creamy white bean soup. The sandwich is toasted under the broiler, not fried in butter, and served open-faced, topped with juicy chopped tomatoes.
When blending hot liquid, first let it cool for five minutes or so, then transfer it to a blender, filling only halfway.
Position a rack about 4 inches from the broiler heat source, and preheat. Bring the wine, rosemary, thyme and 2 cups of the chicken broth to a boil in a covered medium saucepan over high heat. Reduce to a bare simmer.
Puree the beans, shallots, garlic, oil, butter, remaining 1/2 cup chicken broth, 1/2 teaspoon salt, a few grinds of pepper and 1/2 cup of the simmering broth in a blender until completely smooth and emulsified, about 2 minutes.
Meanwhile, lay the bread slices on a rimmed baking sheet, and top evenly with the mozzarella. Broil until the tops are browned and bubbling, 1 to 2 minutes; remove from the oven. Divide the tomatoes evenly among the toasts, and top with the Parmesan.
Remove the herb sprigs from the simmering broth; set aside. Whisk the bean puree into the broth, and return it to a gentle boil. Ladle the soup into bowls, and garnish with the reserved herb sprigs and a few grinds of black pepper. Serve with the cheese toasts.