1. Wash and dry the squash and potato. Peel and chop them into 1 inch pieces. Peel and chop the onion. Peel and mince the garlic and ginger.
2. Melt the butter on medium heat in a large and sturdy pot. Add the chopped onion, garlic, and ginger. Stir in the cumin and black pepper and cook, stirring occasionally, for five minutes.
3. Add in the squash and potato and mix thoroughly with the onion mixture to coat the vegetables. Add the stock, tomato paste and lemon juice and stir to combine.
4. Bring the soup to a boil, then turn the heat down. Cover the pot and simmer for about 25 minutes - just until the vegetables are tender.
5. Remove the pot from the heat and allow the soup to cool some before processing.
6. Puree the soup in a blender, working in small batches. Pour the soup from the blender into a new pot.
7. Place the pureed soup on medium heat and stir in the cream. Season to taste with salt and pepper. Warm through and serve immediately.

Makes 6 to 8 servings.