Add the dried porcini Mushrooms to a bowl and cover with 1 Cup warm water. Soak for 15 minutes. Remove the mushrooms from the soaking water and pour the water through a cheesecloth or fine mesh strainer to filter it. Reserve water.
Put a large stock pot over a medium flame and heat the oil. Add the carrots, onions, celery and rosemary. Cook until the vegetables are soft and the onions are translucent, about 6-8 minutes.
Add in the porcini mushrooms and 2 tablespoons of the reserved soaking water. Cook for 3-4 minutes. Add in the the portobello mushrooms and salt as desired. Cook for 4-6 minutes or until the mushrooms have slightly browned.
Add the water and bring the pot to a boil. Add in the lentils and bouillon cubes and cook until the lentils are tender, about 20-30 minutes. Add the Spinach to the pot and cook until wilted. Serve with crusty Italian bread or Taralli.