Using a medium saucepan, add butter and place over medium heat.

Once butter has melted, add garlic; sauté, stirring often, for 1 minute.

Add flour, salt and thyme; stir until well combined. Continue sauteing for 1 more minute.

Increase heat to medium-high and bring mixture to a simmer. Reduce heat to medium-low and let simmer for 5 minutes, stirring occasionally. Remove saucepan from heat and set aside.

Bring a medium pot of water to a boil.

Meanwhile, using a mandolin, slice the potatoes (peeled or unpeeled) into ¼” thick slices.

Once water is boiling, add sliced potatoes; let cook for 5 minutes. Drain potatoes.

Preheat oven to 375°F.

Spray a 9”x13” casserole dish with nonstick cooking spray. Add several spoonfuls of the milk mixture to the bottom of the dish.

Layer half of the sliced potatoes and onions in the dish. (Note: Feel free to overlap as needed.)

Pour half of the remaining milk mixture on top and then sprinkle half of the shredded cheese on top.

Repeat process using remaining potatoes, onions, milk mixture and cheese.

Bake for 45-50 minutes.

{Optional} Broil the scalloped potatoes for 4-5 minutes, or until top begins to turn golden brown.

Before serving, garnish with chopped fresh parsley and/or sprigs of fresh thyme.