Preheat the oven to 425 degrees F. Lightly butter a sheet of filo pastry. Top with another sheet of filo and lightly butter it. Repeat with remaining filo. Cut sheets in half. Season salmon with salt and pepper and set near the bottom end of each half. Sprinkle on the mint and dill. Fold the sides of the filo slightly over the fish and then roll into a cylinder. Place on a non-stick or parchment-lined baking sheet. Bake 15-20 minutes, until puffed and golden brown. Serve salmon, cutting in half as shown in the photo, on dinner plates with a spoon of tzatziki sauce alongside. Garnish with lemon wedges and dill or mint sprigs.