Preheat oven to 425C.
Peel and cut butternut squash and onion into 1-2 inch pieces. Spread out on a baking sheet. Coat lightly with olive oil and sprinkle with salt and pepper. Roast for 25-30 minutes, or until golden brown.
Cut leeks into 1/2 inch pieces. In a heavy bottomed pot, cook leeks in a small amount of water. When the water appears to evaporate, add a little more, and repeat until the leeks are softened and semi-translucent.
In a high speed blender, combine the cooked butternut squash, onions, bouillon cubes, nutmeg and 7 cups of water. Blend until smooth.
Add your mixture to the pot with the leeks and turn to medium heat.
Rinse lentils, and add them to the pot.
Cook for approximately 30 minutes or until the lentils are soft.
Season with salt and pepper to taste.
Enjoy immediately, or pre-portion for make ahead freezer meals!