In a small saucepan, heat milk, 3 tablespoons (36 grams) sugar, salt, and vanilla bean paste over medium heat, stirring occasionally, until steaming. (Do not boil.)

In a medium bowl, whisk together egg yolks, cornstarch, and remaining 3 tablespoons (36 grams) sugar. Gradually add hot milk mixture, whisking constantly. Pour egg yolk mixture into saucepan, and bring to a boil over medium heat, whisking constantly. Cook, whisking constantly, for 2 to 3 minutes.

Strain mixture through a fine-mesh sieve into a medium heatproof bowl. Cover with plastic wrap, pressing wrap directly onto surface of pastry cream to prevent a skin from forming. Refrigerate until completely cooled, at least 1 hour.