Instructions

1. First, preheat oven to 375ºF and grease a 9×13-inch casserole dish with nonstick cooking spray. Set aside.
2. Next, use a mandolin* to slice all of the potatoes into 1/8-inch thick rounds. We used size 2.0 on our mandolin.
3. Prepare the cheese sauce by heating a medium saucepan over medium/high heat. Add one tablespoon of olive oil.
4. When olive oil is fragrant, add the onion and 1/4 teaspoon salt to the saucepan and sauté for 3 minutes. Add minced garlic and sauté for another 2-3 minutes or until the onion begins to brown.
5. Add the last three tablespoons of olive oil to the pan and let it heat for 30 seconds.
6. Next, add the flour to the saucepan and whisk the oil, onion, garlic, and flour together until it turns into a paste.
7. While continuing to whisk, slowly pour the milk into the saucepan. Continue to whisk the milk over medium heat until the milk begins to thicken.
8. Remove from heat and then sprinkle the cheddar cheese into the saucepan and whisk them together until the cheese melts.
9. Lastly, add the vegetable broth, garlic powder, and Greek Yogurt to the sauce and whisk until combined.
10. Assemble the scalloped potatoes by scooping 1/2 cup of the cheese sauce into the bottom of the casserole dish and spread it around.
11. Create 3 rows of the sliced potatoes, tightly packing them together. With a 9×13-inch casserole dish, you should be able to fit 4-5 lbs. worth of potatoes. 
12. Carefully, pour the cheese sauce on top of the potatoes working the cheese sauce in between each potato round. You can use a knife or fork for this, but it’s important to try and get the cheese in between the potatoes and on top.
13. Cover the scalloped potatoes and bake them at 375ºF for 30 minutes.
14. Remove from the oven, scrape the sides and bake (covered) for an additional 15 minutes.
15. Finally, remove the casserole from the oven one last time and sprinkle the parmesan cheese over the top of the potatoes.
16. Turn the heat to 450ºF and place the casserole dish, uncovered, back in the oven for 5 minutes or until the parmesan cheese starts to brown.
17. Let potatoes rest for at least 5 minutes before serving.