Cook the diced sweet potatoes in salted water until fork-tender. Drain.
Mash the cooked potatoes and cool slightly.
Add milk, vanilla, and eggs to the mashed potatoes along with the flour, baking powder, nutmeg, cinnamon, and butter. Whisk to combine.
Allow the batter to sit for 5-10 minutes while you prepare the apple topping.
In a small, dry skillet toast the pecan pieces for 2-3 minutes until you can start to smell them. Remove and cool.
In a medium-sized saucepan over medium/high heat, cook the apples in the water until the apples have softened and the water has evaporated (approximately 10 minutes).
Reduce the heat to low and stir in the salt, cinnamon, nutmeg, maple syrup, and butter. Stir in the nuts (if desired) and keep warm.
Brush the skillet generously with melted butter.
Drop the pancake batter onto a hot skillet or grill into 6" rounds.
When the outer rims of the pancakes bubble, gently flip the pancakes to brown on both sides but do not overcrowd the pan.
Continue with the remaining batter.
Serve hot with the apple and pecan topping and additional maple syrup if desired.