The night before, add the cashews to a glass of water to soak overnight. If you happen to forget, simply sit the cashews in boiling water for 30 minutes before blending.
Preheat oven to 350F/175C.
Add all of the vegan paremsan cheese ingredients to a blender/food processor and break down to a fine powder. Set aside.
Add the diced onion and garlic to a skillet and saute in 1/4 cup water for 5-6 minutes. Remove from heat.
Add all of the sauce ingredients to a blender and blend until smooth. Taste test and adjust. Just remember one thing: The vegan paremsan is added at the end so the sauce will not taste so much cheesy as simply creamy.
Now begin peeling and slicing the potatoes. Slice the potatoes into 1/8 inch slices. Once finished, begin layering onto a large baking dish.
After the first layer has been laid, pour the sauce over. Add the next layer and pour again. If you have enough potatoes for a third layer, go right ahead! Just be sure the sauce covers the potato slices compeletely. If you begin to run out of sauce, add a bit more non-dairy milk to the blender with the remaining sauce to make just a bit more.
Once the potatoes are fully covered, sprinkle the vegan parmesan cheese all over the top. Add as much as you like!
Bake for 30 minutes covered and then 30 minutes uncovered. I cover my dish with a silicone baking mat but you can also use parchment paper or the traditional aluminum foil.
**If you decide to slice the potatoes before making the sauce, be sure to cover the potato slices in water to avoid browning.