In a large pan, saute the onion with the olive oil, until soft. As you are using so little olive oil you may need to add a splash of water to prevent sticking.
Add the carrots and butternut squash and cook gently for 5 minutes.
Add the mushrooms and cook for another few minutes.
Add the lentils, soya mince and red wine and stir well to combine.
Add the stock, tomato puree and mustard. Give a good stir and bring to the boil. Reduce to a simmer, cover with a lid and leave to cook for between 45 minutes and an hour. Stirring occasionally.
Add the peas at the last minute.The stew should be nicely thickened and flavourful.