|4||each||large egg yolks|
|3||Cup||half and half|
|1⁄2||Teaspoon||pure vanilla extract|
- Prepare an ice bath ( a large bowl with ice and water); set aside.
- In a bowl, lightly whisk egg yolks; set aside.
- In a saucepan, whisk together milk, granulated sugar, cornstarch, and salt. Bring to a simmer (do not boil), and cook, whisking constantly, 3 to 4 minutes. The cornstarch will thicken the mixture.
- Temper the hot mixture into the eggs. Start by whisking a quarter of hot-milk mixture into egg yolks. Then whisk in remaining milk mixture.
- Add in vanilla extract. Strain into a clean saucepan, and cook over medium-high heat, whisking constantly, until custard is thick and bubbles appear in center, 2 to 3 minutes.
- Stir in the butter.
- Transfer to a medium bowl, and cover with plastic wrap, pressing it directly onto surface to prevent a skin from forming.
- Set in ice bath until completely chilled, 30 to 35 minutes. (Filling can be kept in refrigerator, covered with plastic wrap, up to 1 day.)