Cauliflower Alfredo Vegan Scalloped Sweet Potatoes

4 cups reduced-sodium vegetable broth
4 cups water
10 cups cauliflower (about 2 pounds) cut into florets
2 tablespoons avocado oil
2 cups onion chopped
3 tablespoons garlic minced
3/4 cup unsweetened almond milk
1 1/2 to 2 teaspoons sea salt or to taste
Freshly ground black pepper to taste
2 pounds sweet potato peeled and sliced about an 1/8-inch thick (2 pounds total, after slicing)
Fresh parsley for garnish

Preheat your oven to 400°F.
In a large pot, combine the vegetable broth and water, and bring to a boil. Add the cauliflower florets, cover, and cook until fork-tender, about 7 to 9 minutes.
While the cauliflower cooks, heat the avocado oil in a medium skillet over medium-high heat. Add the onion and garlic and sauté, stirring frequently, until golden brown, about 5 to 7 minutes.
Transfer the cooked onion and garlic to a large blender. Using a slotted spoon, transfer the cauliflower to the blender as well, trying to avoid adding excess cooking liquid. Add the almond milk, salt, and pepper. Blend until smooth and creamy, scraping down the sides as needed. Adjust salt and pepper to taste.
Place two layers of sweet potato slices in the bottom of a large, square casserole dish (about 10 inches), slightly overlapping the slices in each layer. Spoon 1/3 of the cauliflower Alfredo sauce (approximately 1 1/2 cups) evenly over the potatoes.
Repeat with two more layers of potatoes, followed by another 1/3 of the sauce. Add a final two layers of potatoes and top with the remaining sauce, making sure to press the potatoes down evenly and spoon some sauce along the edges of the dish.
Cover the casserole dish with foil and bake for 30 minutes. Then, uncover and bake until the top is lightly browned and the potatoes are fork-tender, about 30 to 40 minutes more.
Let the dish stand for 10 minutes to cool slightly. Sprinkle with parsley for garnish before serving.