Preheat oven to 180ºc. Melt butter in frying pan, sautee eschallots and butter on a medium heat until softened. Add in cabbage. Sautee until cabbage is wilted and mixed well with garlic and eschallots. Remove from heat and set aside to cool.
Mix feta, currents and parsley into the cabbage mixture, season with salt and black pepper. Layer 3 sheets of filo pastry with melted butter between each layer. On one side of the layered filo, gather a row of cabbage mixture. This needs to be nice and tight and well formed.
Roll the filo like a cigar shape buttering between each roll. Then turn the cigar into the shape of a snail and tie off with foil.
Bake on tray in preheated oven for approximately 12 minutes or until golden brown on the top and bottom of the spanakopita. Meanwhile, mix together the yoghurt and a small amount of sumac, season with salt and pepper.
Once the spanakopita is cooked, allow to cool slightly. Smear some sumac yoghurt on to a plate, place spanakopita on top and garnish with some thin sliced eschallot and parsley.