Preparation

Make the filling

• Heat the oil in a medium skillet over medium heat. Add the onion and garlic, and cook, stirring occasionally, until softened, about 5 minutes. Add the ground beef and cook, stirring occasionally and breaking up any chunks, until cooked through, about 4 minutes. Add the cumin, cinnamon, paprika, allspice, cayenne, and 1 Tbs. water and cook, stirring occasionally, for another 2 minutes. Season with 3/4  tsp. salt and 1/4  tsp. pepper. Transfer to a bowl and let cool. (The filling may be stored, covered and refrigerated, for up to 1 day.)

Assemble the rolls

• Position a rack in the center of the oven and heat to 400°F. Line a large rimmed baking sheet with parchment.
• Lay out a damp kitchen towel and cover with a sheet of plastic wrap. Unroll the phyllo on a large cutting board and cut in half crosswise so that there are 18 sheets (9×13 inches). Place the phyllo on top of the plastic, and immediately cover with a second sheet of plastic wrap and another damp kitchen towel.
• Remove 2 sheets of phyllo and place them on a large cutting board. Lightly brush the top sheet with melted butter. Cover with a third sheet of phyllo and brush with melted butter.
• Using a pizza cutter or pastry wheel, cut the layered phyllo in half lengthwise and then cut crosswise into fourths, creating eight equal-size rectangles. Working quickly, spread a heaping tablespoon of filling along the top of one of the long sides of each of the phyllo rectangles. Roll up the phyllo and gently press each end to seal. Transfer seam side down to the baking sheet. Lightly beat the egg with 1 Tbs. of water to make an egg wash. Brush the egg wash on top of each roll and then sprinkle with the flaky salt. Repeat with the remaining sheets of phyllo and filling.
• Bake until golden brown, about 14 minutes. Allow to cool slightly, then cut each roll in half on a bias. Serve warm or at room temperature.