Strip the cavolo nero leaves from the stalks then blanch them for 1 minute in boiling water, then drain and place in a tea towel - squeezing out as much moisture as you can.
Fry the onion in 1 tbsp olive oil until soft then add the garlic and cinnamon and fry for a further 2 minutes. Add the cavolo nero and stir to combine then remove from the heat.
Add to a bowl with the crumbled feta cheese and dill, season with black pepper and stir everything to combine.
Take a sheet of filo and place it on a clean work surface. Brush with melted butter and lay another sheet of filo next to it, overlapping them slightly Brush with a little more melted butter. Build up the filo so that you have 4 layers overlapping on top of each sheet of filo.
Spoon the filling in a long line on the bottom edge of the filo. Carefully roll the pastry up and around the filling until you have one long snake of pastry. Next, begin to curl the pastry log up into a spiral shape and place on to a baking tray.
Brush with the egg mixture and cook for 25–30 minutes or until golden brown.
Serve sprinkled with toasted sesame seeds, black pepper and some chopped dill.