Preheat oven to 200ºC/400ºF/gas mark 6.
Add 1 tablespoon olive oil to a pan, add the onion and fry until softened. Add the chopped swede/turnip, parsnips, carrots and garlic and fry for 10 minutes. Sprinkle with the flour and stir. Add the pearl barley, lentils and stock and stir well. Add the soy sauce and mixed herbs and simmer for 15-20 minutes.
Whilst that is simmering, heat a pan of water and simmer the potato slices for 2 minutes to slightly soften. Remove them from the hot water immediately, drain and place in cold water.
Put the vegetable and lentil mix into a large ovenproof dish and add salt and black pepper to taste. Arrange the cooled potato slices over the top and brush with the remaining olive oil.
Place in the pre-heated oven for 45 minutes until thoroughly cooked and the potatoes are browned. Enjoy!