In a mixing bowl of a kitchen aid add the sugar, yeast and water and mix to combine.
Add the flours and 50g of butter then beat with the hook attachment for 8-10 minutes, and the butter is completely incorporated. Transfer dough to a clean bowl dusted with flour, cover with cling film and allow to rise for 45 minutes.
When ready, dust a work surface with flour and place the dough on it. Roll out into a large, even rectangle approx 3mm thick. Using ⅓ of the softened butter spread the surface of the rolled out dough, then cut into 3 equal, long strips. Place these strips on top of one another, the butter side facing up each time. Now fold down the top third of the dough, then the bottom third over the top of that- like you’re folding a piece of paper into 3, brushing the surface of the first fold with a little more butter. Wrap the pastry in cling film and leave in the fridge to firm up for about 10 minutes. Repeat this entire process two more times and set aside in the fridge for the final time.
Roll the dough out to a large rectangle once more and spread evenly with the Nutella (it might help to warm the Nutella up if it is hard to spread). Now cut the dough into 6 long even strips. Fold each strip in half lengthways, then roll up into a tight spiral. Place each spiral into a buttered muffin hole with the cut-side facing up.
Cover with a tea towel and allow the dough to rise for 45 minutes.
Preheat oven to 180c
When ready, remove the towel and bake for 25 minutes. Mix together the caster sugar and cinnamon and sprinkle over the cruffins before serving.