Make the simple syrup first so it can cool. Combine sugar, water, and lemon juice in a saucepan. Bring to a boil, then simmer for about 8 minutes until slightly thickened. Cool completely.
Make the batter. Add warm water, flour, semolina, sugar, yeast, baking powder, dry milk, salt, and optional mahlab to a blender and blend until smooth and lightly bubbly. Rest 20 to 30 minutes until foamy on top. The batter should be thinner than pancake batter.
Cook one‑sided pancakes. Heat a nonstick pan over medium‑low to medium. Pour the batter in one spot and let it spread. Use about 1/4 cup of the batter for medium-sized pancakes, or adjust as you like.Cook until the surface looks dry and covered with tiny bubbles. Do not flip. Transfer to a tray and cover with a towel.
Make the walnut filling. Stir walnuts with cinnamon and just enough simple syrup to bind. The mixture should press together but stay textured.
Make the cream filling. Turn on heat, whisk milk, cream, cornstarch, sugar, and salt until smooth. Cook over medium heat, whisking, until thick and spoonable. Remove from heat, stir in rose water if using, spread in a shallow dish, press wrap on the surface, and cool completely.
For ashta or cream asafiri. Place a pancake bubbly side up, add cream, and pinch halfway to form a cone. Dip the edge in crushed pistachios and drizzle lightly with syrup. These Qatayef should be eaten the same day, as the pancakes and ashta filling won’t stay fresh by the next day.
For sealed qatayef (nuts or cream): Place walnut filling or cream/ashta in the center, fold into a half-moon, and pinch firmly to seal the edge completely.
Fry or crisp the sealed qatayef:Deep fry: In 2 inches of oil for 2–3 minutes per side until deep golden. Transfer to a rack or paper towels to drain.Air fry: At 400°F for 8–10 minutes, spraying both sides with oil.Oven: At 425°F for 15–20 minutes, flipping halfway and spraying with oil.
Dip the hot qatayef briefly in cold syrup, then finish with a sprinkle of pistachios.