Preheat the oven to 425 F/220C/gas mark 7. Line a large baking sheet with parchment paper and set aside.
Prepare butternut squash: Slice the butternut squash widthways into approx. 1'' thick slices, remove the seeds and place on top of a large baking sheet lined with parchment paper. Season with salt and pepper and brush with a little oil.
Roast: Roast in the centre of the oven for 35 minutes until fully cooked and lightly browned (you do not need to turn the slices over). Remove from the oven, set aside for 5 minutes to cool a little then remove the peel. In the meantime prepare the soup base.
Make soup base: In a medium size pot heat up 1 tablespoon of oil, add the garlic and onion and cook gently for 3-4 minutes until softened, stirring often.
Add lentils and stock: Add the lentils, spices and stir. Pour in most of the stock, cover and bring to the boil then lower the hear and simmer for 15 minutes stirring occasionally.
Add squash and puree: Remove from the heat and add the roasted butternut squash. Puree the soup until velvety smooth. Adjust the seasoning and top up with the remaining stock if needed and serve!
Notes
Preparation: An alternative preparation method is to peel then cube the butternut squash before roasting and making the soup (as I have done in butternut squash chili and butternut squash pasta).
Seasoning: You may not need to add any salt into this soup (the stock provides enough salt).
Method: It is important to remove the soup from the heat before adding in the butternut squash in order to preserve all of its rich flavour (the squash will have fully cooked in the oven).
Texture: Puree the soup using either a stick blender or high speed blender (for a super smooth and creamy texture).
Storing: Refrigerate leftover butternut squash lentil soup for up to 3 days.