Preheat oven to 450 degrees.
Wash potatoes and slice them thinly (with a mandoline if you have one). We left the skin on, but you can peel them if you prefer.
Place the sliced potatoes in a baking dish and toss with 1/4 cup oil and your preferred amounts of salt & pepper. Bake at 450 degrees for 20 minutes.
While potatoes cook make a roux in a large skillet or pot by heating the remaining 1/4 cup oil on medium heat, and whisking in 1/4 cup flour. It should take 2-3 minutes.
When roux is mixed well and bubbling, add in 1/2 can full fat coconut milk, 2 cups water, 1 tsp onion powder, 1/4 tsp garlic powder, 1/4 tsp turmeric, and 1/4 tsp lemon juice. Stir well and reduce heat to low after it starts to boil. Stir often, and cook for 10 minutes, then whisk in the 1/2 cup nutritional yeast and 1 tbsp tapioca starch.
Pour cheese mixture over potatoes and bake at 450 degrees for 10 minutes. You can finish it off in the broiler for ~3 minutes if you like to lightly brown the top (watch carefully!). Remove from oven and sprinkle salt & pepper.