Place heavy cream in a medium saucepan, then add seeds from 1 vanilla bean and stir. Bring to a simmer over medium heat, then remove from the heat.
In a separate medium bowl, whisk together large egg yolks, sugar, and DeLallo instant espresso powder. Temper the eggs by adding a couple spoonfuls of the warm cream mixture to the bowl, whisking continuously the entire time to ensure the eggs don’t curdle.
Once tempered, use a spatula to scrape the egg and sugar mixture into the saucepan. Cook over low heat, stirring continuously with the spatula, until the custard thickens enough to coat the back of a spoon. Be careful not to boil the mixture.
Strain the custard through a fine mesh sieve set over a large bowl. Cover tightly, then refrigerate. Can be made up to 2 days in advance.