Spray slow cooker with non stick spray.
Add onions, garlic, potatoes and broth to slow cooker.
Cover and cook on low for 8 hours.
Increase heat to high.
Whisk together cornstarch and evaporated milk until smooth.
Stir cornstarch mixture into slow cooker until blended.
Cover and cook 15 minutes or until thickened.
Stir in cheese until well melted.
Garnish with green onions and bacon.