Preheat the oven to 180°C (fan)/200°C/gas mark 6.
Heat 1 tablespoon of sunflower or vegetable oil in a large pan over a medium heat. Add your chopped onion. Sauté until soft.
Add 2 stalks of chopped celery and a chopped carrot, stir, and reduce the heat to low. Cover with a lid and sweat for 5-10 minutes until starting to soften.
Add the chopped swede and parsnip, stir, cover and sweat for a further 10 minutes.
Stir through two tablespoons of flour then add a bay leaf, a tablespoon of soy sauce, a teaspoon of miso paste, chopped leaves from two sprigs of thyme and 600ml of hot vegetable stock. Stir well.
Bring to the boil, then reduce the heat and cook for 15-20 minutes to thicken. Add the remaining vegetable stock if the sauce become too thick.
Add the cooked lentils and stir through.
Season with salt and pepper to taste.
Transfer to an oven proof dish if needed and cover with slices of potato. Brush lightly with olive oil.
Bake in the oven for 40 minutes until the potatoes are soft and golden brown on top.
Serve with greens or baked beans.