Combine first 7 ingredients in a 4 quart slow cooker.
Cover with lid and cook on high 2 1/2 - 4 hours or until rice is tender and most of the liquid is absorbed.
Whisk egg in a separate bowl. Gradually add 1/2 cup hot rice mixture to egg, stirring constantly to combine.
Add egg mixture back to slow cooker, stirring constantly.
Cook for 1 minute. Turn slow cooker off and let stand 5 minutes.
Stir in cinnamon and sour cream. Serve warm.