Lightly brush the wonton wrappers with oil. Place 8 wonton wrappers into a muffin tray and lay a second wrapper 90 degrees offset with the one underneath. Press into the tray, to form little cups.
Bake in the preheated oven for 7 minutes until wontons are crisp and golden brown.
Meanwhile boil the sweet potato in a saucepan with lightly salted water until soft. Drain and finely mash in a blender or press through a sieve. Stir in cream and season with salt, pepper and nutmeg to taste.
Spoon sweet potato mash into a piping bag and pipe or spoon into the prebaked wonton cups. Place back into the oven and bake for another 5 minutes, until mash is heated through.