Spray the basin of a 6 quart slow cooker with non-stick spray and set aside.
Wash, peel, and thinly slice the potatoes into rounds. They should be approximately 1/4" thick – try to keep the thickness consistent so they cook evenly.
In a medium bowl, whisk together the cream, chicken broth, garlic, salt and pepper.
Layer 1/3 of the potatoes and half of the sliced onions into the bottom of the slow cooker.
Pour 1/3 of the cream mixture over the potatoes.
Sprinkle 1/3 of the cheese over the potatoes.
Repeat.
For the third and final layer, arrange the potatoes slices around the top, pour over the rest of the cream mixture and remaining cheese.
Cover and cook on LOW for 6 hours or HIGH for 4 hours or until the potatoes are tender.
Turn the slow cooker to WARM and let set for 20-30 minutes before serving.
Parsley garnish is optional.