In a bowl beat together sweet potatoes, yogurt, brown sugar, cinnamon, nutmeg, yolks, and salt, to taste, and beat until well combined. Pour this batter into the pie shell and place onto a sheet pan. Sprinkle pecans on top and drizzle with maple syrup.
Bake for 50 to 55 minutes or until the custard reaches 165 to 180 degrees. Remove from oven and cool. Keep refrigerated after cooling.