In a large saucepan, bring enough water to a boil to cover sweet potatoes completely, and add the sweet potatoes. Reduce the heat, and simmer for about 30 minutes, or until softened.

Drain sweet potatoes and place in a large mixing bowl; mash lightly. Add the almond milk. Blend the potato mixture with an electric hand mixer set to medium until smooth and fluffy, about 2 minutes. Season with sea salt and black pepper. Set aside.

Heat 2 Tbs. of vegetable broth in a large skillet over medium heat. Cook the onions over medium-low heat until translucent, then add the garlic and cook for another minute. Add the celery, carrots, peas, corn, thyme and rosemary. Increase the heat to medium-high.

In a small bowl, whisk together the rest of the vegetable broth and arrowroot until smooth, and add to the skillet. When the mixture gets close to boiling, immediately reduce heat. Add sea salt and black pepper, and season to taste.

Remove from heat. Stir in the egg replacer/water combination. Pour the veggie mixture into the bottom of the prepared casserole dish, spreading it evenly across the bottom. Spoon the sweet potato mixture over the vegetables, spreading to cover all the way to the edges of the dish. Sprinkle the top with nutmeg, if desired. Bake in a preheated 375ºF oven until the top is slightly browned, about 40 minutes. Allow to rest 20 minutes or more before serving.