Peel and roughly chop sweet potatoes into large chunks. Place into a large pot and cover with water. Bring water to a boil, reduce heat to medium-high, and gently boil for 10 to 20 minutes, until the potatoes are fork tender.
Preheat oven to 375°F. Lightly spray 9x11 casserole dish or use one that is non-stick.
Prepare the crunchy nut topping: Pour oats into a food processor and pulse until coarsely chopped. In a mixing bowl, add the chopped pecans, oats, cinnamon, salt and stir to combine. Pour in the maple syrup. Mix until combined, using your hands if needed. Set aside.
Drain the cooked sweet potatoes and place in a large mixing bowl and mash until smooth.
Stir in the maple syrup, vanilla, cinnamon, nutmeg, and salt. Adjust to taste if needed. Dump into casserole dish and evenly smooth out.
Sprinkle the crunch nut topping all over the sweet potato mixture, evenly.
Bake, uncovered, at 375°F for 20 minutes, until the dish is hot throughout. Plate and serve immediately.