In a medium bowl, whisk together 1/4 cup sugar and the egg yolks; set aside.
In a medium saucepan combine, remaining 1/4 cup sugar, heavy cream, milk, vanilla bean, and salt, over medium-high heat.
Bring to a simmer.
Using a measuring cup or a ladle, slowly pour about 1/2 cup of the hot milk mixture into the egg-yolk mixture. Whisking constantly, keep adding milk mixture, about 1/2 cup at a time until it has all been added. Pour mixture back into saucepan.
Cook over low heat, stirring constantly with a wooden spoon, until it is thick enough to coat back of a spoon, 1-5 minutes. Pour the fine mesh sieve into a medium bowl, set over ice bath. Whisk in Nutella stirring occasionally until cool.
Cover, and transfer to a refrigerator until completely chilled, at least 1 hour and up to overnight.