The Best Vegan Au Gratin Potatoes

0 Preheat the oven to 350 degrees(F).
1 Slice your potatoes super thin, I like to use a mandolin, but if you don't have one, slice them thin with a knife. 
2 In a large pot, heat the vegan butter on medium high. Once the butter has melted, add the garlic and onion. 
3 Sauté, reducing heat as needed, until the onions are translucent. About 3-4 minutes. 
4 Add the flour to the pot and mix until fully combined with the butter. Let sauté for another minute. 
5 Pour the milk and cream into the pot and whisk to combine, making sure there are no lumps of flour left. Add the salt, pepper and nutmeg, whisk again.
6 Bring to a simmer, reduce heat to medium low and continue to simmer until the sauce is thick and coats the back of a spoon. 
7 Add the cheddar and half the parmesan to the pot. Whisk until the cheeses have fully melted and the sauce is nice and thick.
8 Pour the sliced potatoes into the pot and toss to completely and evenly coat the potatoes in the sauce.
9 Pour the potatoes and all the sauce into a 9x13 inch baking dish. Smooth out. Sprinkle the rest of the parmesan over the top of the potatoes. Cover with foil.
10 Bake for 1 hour then uncover and bake for another 20 minutes. 
11 Let cool for 5 to 10 minutes before serving. It will look a little liquidy when you pull it out of the oven but will thicken when it cools a bit.