In a large saucepan, over a medium heat, melt the butter and add the vegetable oil. Add the onions and cook until translucent. Add the garlic and stir for a few minutes.
Add the chopped butternut square and sweet potato and stir for a couple more mins, stiring to coat with the garlic and onion.
Pour the vegetables into the soup maker, add the stock, parsley and a large pinch of salt and pepper.
Set the soup maker to smooth. When finished, add the cream and serve with a warm buttered baguette.