Place yeast, butter and buttermilk into the Thermomix bowl and warm 2 min/37°C/speed 1.
Add flour and salt and knead 3 min/Interval. Wrap tightly in Silpat mat and allow to prove until doubled.
When dough has risen, preheat oven to 220°C.
Brush some extra melted butter to prepare a rectangular baking dish.
Roll dough into a large rectangle.
Spread the Notella to the very edges of the dough. If it is too solid, warm it a little bit in the microwave. Sprinkle with a few chopped hazelnuts.
Roll dough into large sausage shape starting on the long side of the dough and then cut through using pastry scraper. Turn filling side up and arrange in baking dish next to each other so there are no gaps.
Brush with extra melted butter, top with some more hazelnuts and place into the oven. Reduce temperature to 200°C and cook for 18 minutes or until golden.
Drizzle with a little melted chocolate if you can take it!