01 - Preheat the oven to 375°F. Line a baking sheet with parchment paper and set aside.
02 - In a mixing bowl, combine the chopped artichoke hearts, spring onions, dill, grated Graviera, and crumbled feta. Season with black pepper and sea salt, then stir until evenly incorporated.
03 - Lay one filo sheet flat on a clean work surface and brush lightly with melted butter. Place a second sheet on top and brush again with butter.
04 - Using a sharp knife, cut the layered filo sheets lengthwise into 4 equal strips. Repeat this process with the remaining filo sheets to yield 16 strips total.
05 - Place 1 heaping tablespoon of the artichoke and cheese mixture at the bottom end of each strip. Fold the corner over the filling to form a triangle, then continue folding up the strip in a triangle pattern until the entire strip is wrapped around the filling.
06 - Brush the tops of each folded puff with the beaten egg. Sprinkle with sesame seeds if desired.
07 - Arrange the puffs on the prepared baking sheet. Bake for 20 to 25 minutes, or until the pastry is golden brown and crisp.
08 - Remove from the oven and allow the puffs to cool slightly before serving. Best enjoyed warm.