Soften your nutella by microwaving for a few seconds, it doesn't take much. If you keep your nutella in the fridge, take it out a couple hours before so it's not quite so cold.
Heat your cream to just under boiling. Remove from heat and add vanilla extract.
Meanwhile cream together egg yolks and sugar with a fork until smooth. Try not to get air into the mixture.
Preheat oven to 325. After cream has had some time to cool a bit (10ish minutes is plenty) SLOWLY pour the cream into the eggs, stirring with the fork to combine. Try not to get air into the mix. And don't pour too fast or you will cook your eggs.
Add nutella to the custard and mix with the fork to distribute evenly. It may take a bit for the heat to soften the nutella enough. Don't give up until the custard looks and feels smooth.
Evenly divide custard into 8 ramekins. Place ramekins in a lasagna pan, then fill the pan with lukewarm water until it comes most of the way up the outside of the ramekins.
Bake 30-60 minutes. The time will depend on the shape of your ramekins. Custard is done with it is set but still jiggly in the center.
Remove ramekins from water bath and allow to cool for an hour. Then cover with plastic wrap and refrigerate a minimum of 4 hours, but not more than 3 days.
When ready to serve, top each with 1-2 tsp sugar and caramelize the sugar with a blowtorch, or under the broiler. You want to melt and brown the sugar without it burning.