Peel potatoes and slice 1/4-inch thick with a mandolin or chef’s knife.
Cover sliced potatoes with water in a large bowl while you make the sauce.
Make the Sauce
To a saucepan over medium-high heat, add water and chicken base. Whisk together, then whisk in heavy whipping cream.
Mixture should be getting hot at this point. Sprinkle in the parmesan cheese while whisking constantly.
Add half of the shredded cheddar, one handful at a time, whisking continuously. Mixture should be boiling by now. Turn heat down to low and simmer for 2 minutes, whisking occasionally. Remove from heat and set aside.
Assemble
Spray the crock of the slow cooker with non-stick cooking spray.
Add a single layer of sliced potatoes to the bottom of the crock pot. Season to taste with garlic salt and pepper.
Add a layer of shredded cheese.
Ladle on a layer of cheese sauce, enough to where you can’t see the potatoes.
Repeat these layers 2 more times, ending with cheddar cheese.
Cover the slow cooker and cook on High for 3-4 hours, or until potatoes are fork tender.TIP - You may need to skim some extra liquid off the top due to the amount of steam that is created while cooking.
Russet potatoes work perfectly here. You can substitute the Russet with another starchy potato such as Yukon gold. The starch content plays an important role in scalloped potatoes as it helps thicken the cream sauce. A mandolin will help a ton in this recipe as the thinner the potatoes are sliced, the quicker they will cook.
As with most recipes, I highly recommend shredding the cheese yourself with a box grater. This will prevent the cheese sauce from being grainy. Plus, blocks of cheese don't contain anti-caking agents like pre-shredded cheeses do which prevents them from melting as well.
We use a concentrated bouillon base for most of our recipes instead of broth or stock. It’s convenient, takes up a lot less space, and is easily reconstituted with water. You can certainly use broth or stock instead.