01 -
Spray a 9x13 pan with nonstick spray. Preheat oven to 350°F. Wash, dry and peel potatoes. Slice them very thin (⅛-inch) using a mandolin.
02 -
In a large saucepan over medium-low heat, melt butter. Add onion and garlic and cook until soft.
03 -
Add flour and cook 2 minutes longer. Reduce heat to low and slowly whisk in chicken broth, then milk. Increase heat to medium and stir constantly until mixture boils and thickens.
04 -
Season with salt and pepper to taste. Remove from heat and stir in ½ teaspoon thyme and cheddar cheese until melted.
05 -
Place half the sliced potatoes in the prepared pan. Season with salt and pepper. Pour half the sauce over potatoes. Add second layer of potatoes, season again, and pour remaining sauce on top. Sprinkle with fresh thyme.
06 -
Cover with foil and bake for 45 minutes.
07 -
Remove foil and bake another 30 minutes until golden and bubbly.
08 -
Remove from oven, garnish with fresh thyme, and let rest 10-15 minutes before serving.