Place sweet potatoes in a pot, cover with water, and bring to a boil. Reduce heat and simmer until very tender. Drain and let cool.

Peel and lightly mash the sweet potatoes once cooled.

Combine mashed sweet potatoes, vanilla extract, cinnamon, and nutmeg in a food processor. Process until smooth, adding condensed milk gradually to reach the desired consistency.

Spoon the pudding into a bowl or individual dishes, and garnish with walnuts. Refrigerate for at least 2 hours before serving.