Preheat oven at 400ºF.
Bake sweet potato till soft, allow to cool slightly, peel, mash and set aside (leftovers work well). While sweet potato is cooking, squeeze sausage from casing in small pieces and brown in a skillet over medium heat. Place the Italian sausage, mashed sweet potato, dried parsley, dried sage, brown sugar, stone ground mustard, chopped toasted pignoli nuts and quartered mission figs in a bowl and gently fold together with a wooden spoon.
Cut puff pastry into 4ths. Place 1/4 of mixture on one of the puff pastry sheet pieces. Brush the edges of the pastry with egg yolk mixture. Fold over the puff pastry sheet one corner to the next making a triangle shape. Pinch the edges with a finger or use fork that has been dipped slightly in flour.
Place turnovers on a baking sheet leaving a little space in between. Brush each turnover with egg mixture. Split the tops of the turnovers lightly with a criss-cross shape. Bake in oven until pastry is a deep golden brown color.