1cupmilk or heavy cream (alternate milks may be used as well)
Melt the butter in an 8-quart stockpot. Add the onion and salt. Sauté over low heat until soft and translucent but not browned, 4-6 minutes. Add the curry, cinnamon, and nutmeg. Stir to warm the spices in the butter, 30 seconds.
Add the prepared squash, apples, and stock. Bring to a boil, then reduce to a simmer. Cover and cook until the squash and apples are soft, 30-40 minutes.
Remove from the heat and purée in a countertop blender or with an immersion blender until smooth and creamy.