1. Bake potatoes at 400 degrees for 1 hour or until tender.
2. Cool 10 minutes. Increase oven temperature to 450 degrees.
3. Fit pie crust into a 9-inch pie plate.
4. Fold edges under and crimp.
5. Prick bottom and sides of pie crust with a fork.
6. Bake at 450 for 9-11 minutes or until lightly browned. Reduce oven temperature to 375.
7. Cut potatoes in half lengthwise.
8. Scoop out sweet potatoes into a medium bowl.
9. Mash until smooth.
10. Stir in butter and next 4 ingredients until well combined.
11. Whisk egg yolks until thick and pale.