Pour ¾ cup cream into a small saucepan. Add sugar (1/3 cup) to saucepan.
Pour remaining ¾ cup cream into a large bowl. Add milk and vanilla to bowl
Soften gelatin by sprinkling it over ¼ cup cold water in a small bowl
Bring saucepan of cream/sugar to a simmer over medium heat. Do not boil.
While whisking, add the softened gelatin to the saucepan of hot cream mixture, stirring constantly until gelatin is dissolved in the warm liquid
Pour warm gelatin/cream mixture into the bowl with the cold liquids. Whisk together until completely combined
Using a ladle, fill 6 ramekins or custard cups with the mixture. Cover with plastic film and refrigerate until set (at least 2 hours )
To Serve: run a small knife around the rim of each cup, then dip bottom of ramekin quickly into a shallow bowl of hot water. Cover ramekin with a dessert plate and invert. Panna Cotta will gently release onto the plate.
Place cream, milk and sugar in a saucepan over low heat, stirring constantly until hot. Do not boil.
Add the Nutella and the butter, stirring until melted and all ingredients are blended into a smooth sauce.
Allow to cool at room temperature. Consistency should be pourable at serving time
Simmer all ingredients in a saucepan for about 5 minutes
minutes or until thickened
Refrigerate about 30 minutes