Step 1

Preheat oven to 400 and spray a 7×11 dish with nonstick spray. a 9×13 will also work, it will just be thinner.

Step 2

Slice potatoes thin, about 1/8th inch thick. Layer half of the potatoes on the bottom of the pan, in overlapping layers.

Step 3

In a sauce pan, turn on medium high heat and add butter. Once melted, add in onion and saute for a few minutes until slightly softened. Add in garlic, thyme, salt, pepper, and cayenne and stir until combined well.

Step 4

Whisk in milk and arrowroot powder, and bring to low simmer for a few minutes, stirring occasionally. The mixture should begin to thicken. Turn off heat.

Step 5

Add in 1/3 of the cheddar cheese to the milk and stir to melt.

Step 6

Pour half of the cheese sauce over the first half of the potatoes and spread out with spoon.

Step 7

Add the rest of the potatoes on top in a stacked pattern. Pour the rest of the cheese sauce on top of the potatoes, and spread evenly with spoon.

Step 8

Top with remaining cheese and bake for 40-45 minutes or until golden brown and bubbly.