Yield: 1 1/2 quarts
Once the vegetables are very soft, remove from heat and place the mixture in a blender. Blend to a fine consistency and return to the soup pot over low heat. Stir in the remaining chicken broth and season with salt and pepper. Bring to a boil, add the reserved porcini caps and simmer 20 minutes.
In a small mixing bowl mix the mascarpone with the rosemary and the pepper. Smear the mascarpone mixture on to the baguette slices and place 3 smeared slices in each of 4 bowls. Ladle the soup over the crostini serve immediately.