Preheat oven to 375. Saute the onions in olive oil for 5 minutes and during the last minute add the garlic. Cut the potatoes into small bite sized cubes and place into a large bowl. Add the onions to the potatoes and mix.
In a 4 cup measuring cup, add the almond milk, nutritional yeast, cornstarch and salt. Mix until particles have disolved.
Finely grate the vegan Parmesan cheese till you have about 1/2 cup. More is better and you can also wait to grate it when you add it to the pot directly.
Grease a 3 quart baking dish. Add 1/3 of the potato mixture, sprinkle with salt and pepper, add 1/3 of the cheese and slice up 1 Tbsp vegan butter on top. Repeat this process 2 more times.
Pour the liquid mixture onto the potatoes. If there are still some clumps in the liquid, discard them. The liquid should almost cover the top layer of potatoes.
Bake with a cover for 40 minutes. Remove cover and bake another 40-50 minutes. Let pot rest for 5 minutes and serve.
