Heat the olive oil in a skillet over medium heat, and saute the onion and garlic until tender.
In a large pot, mix the onion mixture, potatoes, carrots, and split peas. Pour in the vegetable broth. Bring to a boil, reduce heat to low, and simmer 1 hour.
In a blender or food processor, blend the tofu and spinach until creamy, and mix into the pot. Season with basil, salt, and pepper. Continue cooking 1 hour. If the soup becomes too thick, add water. Serve hot and enjoy.