Step 1

Preheat your oven to 350 degrees F. Spray a 9 x 13 baking dish with cooking spray. Set aside.

Step 2

Melt butter in a medium saucepan over medium heat. Add onions and cook until onions are softened (about 4 to 5 minutes), stirring frequently.

Step 3

Add garlic and cook until fragrant, about 30 seconds (stirring constantly).

Step 4

Add thyme and stir to combine.

Step 5

Add flour, salt, pepper and nutmeg. Cook for 1 minute, stirring constantly.

Step 6

Slowly pour in half-and-half, while continuing to stir. Slowly pour in chicken stock and continue to stir.

Step 7

Increase heat to medium high and bring to a gentle boil (while continuing to stir). Boil for 2 minutes, or until mixture is thickened. Reduce heat as necessary to maintain a gentle boil (medium to medium low). Remove from heat.

Step 8

Arrange ½ of the potatoes in the bottom of prepared baking dish. Sprinkle potatoes with desired amounts of salt and pepper. Pour ½ of sauce over potatoes as evenly as possible.

Step 9

Arrange remaining half of sliced potatoes over cream sauce and sprinkle with desired amounts of salt and pepper. Pour remaining cream sauce over potatoes. Sprinkle evenly with Parmesan.

Step 10

Cover with aluminum foil that has been sprayed with cooking spray (this helps the cheese from sticking to the foil).

Step 11

Bake for 50 minutes. Remove the aluminum foil and bake for an additional 40 minutes, or until potatoes are tender.

Step 12

If desired, broil on high for 1 to 2 minutes (watching carefully) or until golden brown.

Step 13

Sprinkle with additional fresh thyme leaves when serving, if desired.