In a large bowl, whisk together the eggs, buttermilk, and oil. Stir in the pancake mix and nutmeg until just combined. Fold in the sweet potato. If the batter seems too thick, add more buttermilk until it reaches the desired consistency (it should be thick but still pourable). Place a large, greased griddle or pan over medium-high heat. Working in batches, spoon the batter onto it and cook until the surface of the pancake is covered with bubbles, 2 to 3 minutes. Flip and cook the other side until golden, 1 to 2 minutes more. Serve, topped with honey-cinnamon butter and a little maple syrup.