Preheat the oven to 400 degrees Fahrenheit.
Slice all of your root vegetables (potatoes through carrots) as thinly as possible in a mandolin or using a knife. Set aside.
2 sweet potatoes, 1 rutabaga, 3 turnips, 4 parsnips, 4 carrots
Heat the olive oil in a small saucepan. Add the onion and cook for 3 minutes or until translucent and lightly browned. Stir in the oregano, thyme, and garlic, Cook for 1 more minute.
2 tablespoons olive oil, 1/4 cup chopped onion, 1 teaspoon dried oregano, 1 teaspoon dried thyme, 2 cloves garlic
Add the corn starch and stir until onion mixture is well coated. Pour in the almond milk and stir with a whisk. Bring to a simmer and stir constantly until mixture starts to thicken - about the consistency of alfredo sauce.
2 tablespoon corn starch, 2 cups plain
Whisk in the nutritional yeast and turn off the heat.
1/4 cup nutritional yeast, Dash of salt and ground black pepper
Arrange the sliced vegetables in a 9"x11" baking pan. Pour sauce evenly over the vegetables.
Cover with aluminum foil and bake for 45 minutes.
Make the gratin topping by putting the almonds in the food processor and blending until they are the consistency of bread crumbs. Add the nutritional yeast, salt, and pepper and pulse a couple more times until mixed.
Dash of salt and ground black pepper, 1/2 cup nutritional yeast, 1/2 cup almonds, 1/2 teaspoon dried parsley
Remove gratin from the oven and take off the foil. Sprinkle topping evenly over the vegetables in the baking dish.
Cover the baking dish with aluminum foil and bake for another 15 minutes or until vegetables are tender when pierced with a knife or fork.