In a Dutch oven cook squash in boiling water for 2 minutes; drain and place in a bowl of ice water to cool quickly. Drain again; pat dry with paper towels.
In a medium bowl combine the next three ingredients (through coriander). Stir in 3/4 cup of the cheese.
Line a 3 1/2- or 4-quart slow cooker with a disposable slow cooker liner. Layer half of the squash, potatoes, leeks, and sausage in prepared cooker. Top with half of the soup mixture. Repeat layers.
Cover and cook on low about 6 hours or on high about 3 hours or until vegetables are tender. Turn off cooker. If possible, remove crockery liner from cooker. Sprinkle with the remaining 1/4 cup cheese. Let stand, uncovered, 10 minutes. Sprinkle with pepitas and/or cilantro.