Golden rum adds a mellow sweetness to this rich cream. If you can't find it, use brandy or Cognac instead. This is the filling for the Pastry Wreath with Orange-Rum Cream.
Heat milk, 1/2 cup sugar, and vanilla seeds and pod in a small saucepan over high heat until steaming (do not simmer). Immediately remove from heat. Discard vanilla pod.
Whisk egg yolks with remaining 2 tablespoons sugar in a medium bowl until thick. Sprinkle in flour and cornstarch, and whisk until combined.
Whisk half the hot milk mixture into yolk mixture. Return entire mixture to saucepan with remaining milk mixture, and bring to a boil, whisking constantly and quickly to prevent scorching. Cook, continuing to whisk, until thickened, about 2 minutes. Strain pastry cream through a fine sieve into a bowl.
Add butter and stir until melted. Stir in rum and orange zest. Press plastic wrap or waxed paper directly onto surface of pastry cream to prevent a skin from forming. Refrigerate until chilled, about 2 hours.
Pastry cream can be refrigerated, covered, for up to 3 days.