Add your olive oil to a large frying pan on a medium to high heat. Add your onions, garlic and carrot and fry for around 5 minutes until they start to soften.
Next add your mushrooms and leeks and mix well. Fry for another 5 minutes until they start to soften.
Add your lentils followed by chopped tomatoes, vegetable stock, Worcestershire sauce, soy sauce, red wine vinegar, thyme, sage, salt and black pepper. Mix well and leave to simmer for around half an hour on a low to medium heat, mixing regularly.
Meanwhile add your peeled and chopped potatoes to a large saucepan. Add water and bring to a boil on the hob. Boil until the potatoes are soft.
Once the potatoes are soft drain, add butter and dairy free milk and mash (I actually use an electric whisk to mash my potatoes as it works really well!).
Pre heat your oven to 180C. To a large oven proof dish add the lentil and mushroom mixture followed by the mash potato. Use a fork to score lines across the top and place in the oven for around 40 minutes until cooked through. Serve warm and enjoy.