Heat oven to 350 degrees.
In large bowl, mash sweet potatoes with butter.
Add condensed milk, cinnamon, nutmeg and salt, mixing well with a whisk or hand mixer.
Stir in eggs.
Pour into prepared pastry shell.
Bake 50 to 55 minutes or until knife inserted near center comes out clean.
Pie can be served warm with whipped cream. Makes 1 (9-inch) pie. Store leftovers in refrigerator.