How to Make It
In a medium saucepan over medium heat, combine cream, milk, and crumbled cornbread. Bring to a simmer. Meanwhile, in a medium bowl, whisk sugar and egg yolks until pale and thick. When cream mixture reaches a simmer, slowly ladle 1/2 cup of it into egg mixture, whisking constantly. Repeat with another 1/2-cup ladleful. Reduce heat to low, whisk warmed egg mixture into saucepan, and cook, whisking, until mixture thickens a bit, about 5 minutes.
Pour mixture into a medium bowl, stir in vanilla and buttermilk, cover with plastic wrap (letting the wrap sit directly on the mixture's surface), and chill at least 2 hours and up to 1 day.
Strain chilled mixture through a fine mesh strainer; then transfer to an ice cream maker and freeze according to manufacturer's instructions. Serve immediately or transfer to an airtight plastic container and freeze up to overnight. Top with blueberry preserves, if desired.