Step 1

Melt butter in a large saucepan over medium heat. Add onion; cook, stirring occasionally, until it begins to soften, about 4 minutes. Add squash, and cook, stirring occasionally, until soft, about 10 minutes.

Step 2

Add apples, salt, cumin, coriander, ginger, cayenne, black pepper, stock, and the water (just enough to cover). Bring to a boil. Reduce to a simmer, and cook until vegetables are very soft, about 30 minutes.

Step 3

Puree in batches in a food processor or blender until smooth, and return to saucepan. Heat over low, thinning with more water if necessary. To serve, ladle into shallow bowls; garnish with diced apples, jalapeno slices, and sour cream if desired.