Pre-heat oven to 400°F. Grease a 9 x 13-inch baking dish with gluten-free cooking spray.
In a medium saucepan, melt the butter over medium-high heat.
Add the milk to the pan and whisk until combined with the butter.
Whisk the gluten-free flour into the milk mixture.
Add the salt, pepper, onion powder, garlic powder, and dried thyme to the cream sauce, stirring until combined.
Add the broth to the pan, and whisk until combined. Cook for 1-2 minutes until the sauce just barely begins to simmer around the edges of the pan and thickens. Remove from the heat, once the sauce has thickened.
Spread half of the sliced potatoes in an even layer on the bottom of the greased pan.
Top evenly with half of the cream sauce.
Sprinkle the Parmesan cheese and 1 cup of the shredded cheddar cheese over the top of the first layer of potatoes and cream sauce.
Top evenly with the remaining sliced potatoes, the other half of the cream sauce, and the remaining 1 cup of cheddar cheese.
Cover the baking dish with aluminum foil and bake for 30 minutes.
Remove the foil and bake uncovered for another 30 minutes, or until the potatoes are cooked through.
Allow the potatoes to cool for a few minutes before serving. Serve warm.
This recipe was originally created for my cookbook, The Everything Gluten-Free & Dairy-Free Cookbook. I did not use dairy-free cheese in the original recipe. You can choose to use the dairy-free/vegan cheese or leave it out. If you want the potatoes to be a little crispier, broil for a few minutes. The scalloped potatoes without cheese are just as delicious.
Store leftovers in an airtight container and refrigerate.
Reheat in the microwave or in the oven in an oven-safe dish at 350°F for 15-20 minutes until the potatoes are warm.
For the dairy-free option, I used Smart Balance butter, unsweetened almond milk, Violife cheddar cheese shreds, and Follow Your Heart Parmesan. You can also leave the dairy-free cheese out of the recipe.
For the vegan option, use gluten-free vegetable broth and the dairy-free butter and cheeses option.