Start by prepping all the vegetables. Peel and dice the onion, garlic, carrots, potatoes, swede and parsnip. Chop the celery.
Heat the olive oil in a large soup pot over medium heat. Add the onion, garlic, carrots and celery. Cook for about 5 minutes, stirring occasionally, until the vegetables have softened.
Stir in the tomato paste, thyme, oregano and basil. Cook for 1–2 minutes until fragrant.
Add the potatoes, swede, parsnip and dried soup mix. Stir well to combine.
Pour in the vegetable stock and water. Season with salt and pepper, then mix through. Bring to the boil.
Once boiling, reduce the heat to a low simmer, cover, and cook for about 45 minutes or until the lentils and barley are tender.
Add the frozen peas and stir through. Let them heat for a few minutes, then taste and adjust the seasoning if needed.
Serve hot, topped with chopped parsley if desired.