Heat the oil in a large pot over medium high heat, then gently fry the onion, bay leaf and garlic for 5 minutes, or until onions are translucent. Add the peas, barley, salt and water. Bring to the boil, then reduce heat to low. Simmer for 2 hours, stirring occasionally.
Heat the oil in a large heavy-based saucepan over a moderate heat. Add the onion and garlic to the pan and cook gently for about 7 minutes, stirring frequently until the onion is soft and golden. Add the carrots and continue to cook for 4–5 minutes, stirring frequently until just beginning to soften.
Add the carrots, celery, potatoes, parsley, basil, thyme and pepper. Simmer for another hour, or until the peas and vegetables are tender.
Stir in the split peas, stock, tomato paste, sage and seasoning and bring to the boil. Reduce the heat, then cover and simmer for 30 minutes.
Add the pasta and cook for a further 15 minutes until the pasta and split peas are tender. Serve in deep bowls sprinkled with grated parmesan.