Pre-heat your oven to 200°C (390°F)
Cut the ends off the butternut squash and halve lengthwise
Scoop out the seed from the squash
Coat the squash in olive oil, season with salt and pepper and place in a roasting pan
Wrap garlic cloves coated olive oil with tin foil, place in the the roasting pan
Peel and halve the onion and cut off the root end, place alongside the squash cut side down
Place roasting pan in pre-heated oven and roast for approximately 50 minutes
When the vegetables are finished cooking scoop the squash out of the peel and add to a blender along with the onions and garlic (if your blender in small this can be done in batches).
Add a splash of stock to the blender and blend until smooth.
In a pot combine the blended vegetables and the remainder of the stock
Bring pot to a simmer over medium low heat
Add the lentils and cook for 15-20 minutes or until the lentils are soft