Preheat oven to 375° Fahrenheit. Spray a 9 x 13 inch baking dish with cooking spray and set aside.
Place potatoes in a large stock pot and cover with water. Bring to a boil, reduce heat, and simmer for 25 to 30 minutes, until fork tender. Drain and transfer to a large bowl.
To the bowl with the sweet potatoes, add the almond milk, brown sugar, spices, and vanilla extract. Beat with an electric mixer on medium-high until fairly smooth. Add the egg and beat again until incorporated. Transfer potato mixture to the prepared dish.
Sprinkle the pecans evenly over the surface of the potatoes, followed by the marshmallows and salt. Bake for 25 minutes, until the marshmallows have melted.
NOTE: You can toast the pecans whole in the oven or a toaster oven at 375° for 6 minutes.