Au Gratin Potatoes

Make the creamy sauce.

1. Melt the butter in a large skillet on the stove over medium-high heat.
2. Add the diced onions, cook for 4 minutes, then add the minced garlic and cook for an additional minute.
3. Add the flour to the skillet, stir to combine everything, and cook for an additional 1-2 minutes.
4. Add the chicken broth to the skillet and whisk to combine everything.
5. Reduce the heat on the stove to medium-low and slowly stir in the half and half.
6. Continue to cook, while stirring, until the mixture comes to a gentle boil.
7. Stir in the salt, thyme and black pepper. Remove the creamy sauce from the heat and set it aside.

Prepare the potatoes.

1. Preheat the oven to 350°F.
2. Thinly slice all of the potatoes using a sharp knife or mandoline. I used this mandoline on setting 3 to slice the potatoes, while wearing these cut-resistant gloves. 
3. Grease a 9” x 13” casserole dish with butter or cooking spray.
4. Place ⅓ of the potatoes in the bottom of the prepared casserole dish, sprinkle about ½ teaspoon salt evenly over the potatoes, then pour ⅓ of the sauce over the potatoes. Sprinkle ½ cup shredded cheddar cheese and ½ cup shredded gruyere cheese over the sauce.
5. Repeat another layer of potatoes, salt, cream sauce and cheese, then another layer of potatoes, salt and cream sauce. Reserve the remaining cheese for later.
6. Cover the casserole dish with a large piece of aluminum foil and bake for 45 minutes.
7. Uncover the baking dish, sprinkle the remaining 1 cup cheddar cheese and 1 cup gruyere cheese over the potatoes, and bake for an additional 20-30 minutes.
8. Turn the oven from bake to broil and continue cooking 2-3 minutes, or until the top of the cheese starts to bubble.
9. Remove from the oven and let the potatoes rest for 15 minutes before serving.