Scalloped Potatoes with Crispy Cheese Crust

Preheat oven at 400 degrees.
In a large skillet, on medium low heat, add cooking oil and fry shallots so they are nice and caramelized, around 15-30 minutes. Remove shallots from skillet.
Before making your roux, heat up the milk in a separate small saucepan until it gets hot but not boiling, or it will curdle.
In the same skillet used for frying the shallots, on medium heat, make your roux by adding butter and let it melt, then add flour and whisk for 30 seconds.
Then add the warm milk, cheese, salt and pepper and whisk for a minute until the sauce thickens.
In a buttered casserole dish, add caramelized shallots to the bottom of the dish.
You can either create flat layers of potatoes in your casserole dish (around 4 layers) or you can do rows where they are stacked upright, leaning on top of each other. The latter is my preferred method.
Pour cheese sauce over potatoes. If doing the flay layers, you will apply cheese sauce on top of each layer. If doing stacked upright, then you will just pour the cheese sauce all over the potatoes, and with a rubber spatula spread cheese sauce evenly.
Top with ¾ cup shredded cheddar cheese on top. If you love lots of cheese then feel free to add more.
Bake for 60 minutes at 400 degrees. You will know it’s ready is when the top layer is a nice golden brown. Around the 45 minute mark, keep a close eye on it as every oven is different.
Remove from oven and let it rest for at least 15 minutes before cutting into it.
Garnish with thyme (optional).