Heat the olive oil in a large pot over medium heat. Add the onions, carrots, potatoes, mushrooms, and garlic and cook until the onions go clear and the mushrooms are tender, about 7 to 10 minutes.
Stir in the water and tomato paste. Bring to a simmer.
Add the beans, pasta, barley, corn, peas, sausage, herbs, and salt. Simmer for 20 minutes or until the pasta and barley are tender. Dust with cayenne pepper, adjust seasonings, and serve.
Notes
You can freeze any leftover soup. Allow soup to cool and freeze in an airtight container for up to 3 months.