01 -
Spray a 9x13 inch baking pan with nonstick spray and preheat the oven to 350°F.
02 -
Wash, dry, and peel the potatoes. Using a mandoline, slice them thinly to ⅛ inch thickness.
03 -
In a large saucepan over medium-low heat, melt butter. Add diced onion and minced garlic, cooking until soft and translucent.
04 -
Stir in the flour and cook for an additional 2 minutes to eliminate raw taste.
05 -
Reduce heat to low and slowly whisk in chicken broth, followed by milk. Increase heat to medium and stir constantly until the sauce boils and thickens. Season with salt and pepper.
06 -
Remove from heat and fold in ½ teaspoon dried thyme and grated cheddar cheese until melted and smooth.
07 -
Layer half of the sliced potatoes in the prepared pan, seasoning with salt and pepper. Pour half of the sauce over the potatoes, then repeat layering with remaining potatoes and sauce. Sprinkle fresh thyme on top.
08 -
Cover the dish with foil and bake in preheated oven for 45 minutes.
09 -
Remove the foil and bake an additional 30 minutes until golden and bubbly.
10 -
Remove from oven, garnish with fresh thyme, and let rest for 10 to 15 minutes before serving.