How to Make It
Combine 1/2 cup sugar and egg yolks in a large bowl, stirring with a whisk until mixture is pale.
Combine half-and-half, evaporated milk, and remaining 1/2 cup sugar in a medium saucepan; bring to a gentle boil over medium heat, stirring occasionally, until sugar is dissolved. Gradually add half of hot milk mixture to egg mixture, stirring constantly with a whisk; return milk-egg mixture to pan. Cook over medium-low heat 6 minutes or until mixture thickens and coats a rubber spatula, stirring constantly with spatula. Strain through a sieve into a large bowl set over a larger ice-filled bowl. Let stand until cool, stirring occasionally. Add buttermilk, stirring with a whisk. Pour into an airtight container; cover and chill 30 minutes.
Pour mixture into the freezer can of an ice-cream freezer; freeze according to manufacturer's instructions. Add pie just before removing ice cream and while machine is still churning. Remove ice cream to an airtight container; freeze 3 hours or until firm.