Soften porcini mushrooms in cold water (squeezing them and changing water a few times). Keep the water. Prepare or preheat vegetable soup. Sauté the sausage and then add mushrooms and some mushrooms water. Add all these ingredients to the vegetable soup.
Slice bread. Alternate bread slices, hot soup and Parmigiano Reggiano in the same way you would when making lasagna. Lastly, pour the hot bouillon cube broth over the dish and leave to rest for 10 minutes to allow bread slices to absorb the broth. Oven cook at 392°F for 20 minutes.