Best Winter Vegetable Soup

For the squash:

• 1½ pound cubed kabocha or butternut squash
• 2 tablespoons olive oil
• 1 teaspoon salt
• ⅛ teaspoon black pepper

For the rest of the soup:

• 2 tablespoons olive oil
• 5 tablespoons tomato paste (3 oz, or 1/2 a can)
• 1 large onion (1 large onion = about 8 oz/225g, diced)
• 10 cups water
• ½ cup yellow split peas (rinsed and drained)
• 2 large carrots (diced)
• 8 ounces button or cremini mushrooms (diced)
• 1 pound cabbage (roughly chopped)
• ½ teaspoon dried oregano
• 1 teaspoon dried thyme
• 6 dried bay leaves
• 1 teaspoon salt (or to taste)
• ½ teaspoon ground black pepper