Heat the cream, half-and-half, vanilla, and sugar in a saucepan over high heat, whisking, for 3 minutes. Dissolve the cornstarch in the bourbon.
When the bubbles form around the edges of the cream, whisk in the bourbon mixture. As the cream boils up, remove the pot from the heat and continue whisking vigorously until thoroughly blended and slightly thickened. Place over low heat and simmer for 1 minute. (This is not a thick cream sauce; it’s meant to be fairly thin.) Serve immediately or store, refrigerated, in an airtight container for up to 24 hours. Reheat in a double boiler.
Yield: 2 cups