Combine 200 ml of cream, milk, sugar and Nutella in a small saucepan and set on medium heat.
Stir to dissolve the sugar and Nutella. Remove from the heat just before it reaches boiling temperature.
In another saucepan warm up the remaining 50 ml of cream.
Drain the gelatin and squeeze any excess water. Add gelatin to the hot cream and stir to dissolve. Pour gelatin mixture into Nutella mixture and sitr to combine.
Divide panna cotta between serving cups and place in the fridge to set. Resting time may vary depending on serving cup size; budget in about 4 hours to properly set. Wait until it has fully set to decorate.
Lightly warm 2 tbsp Nutella and add to a piping bag. Pipe nutella swirls over each panna cotta. Top with hazelnuts.