To make the ashta: Add the half-and-half and condensed milk to a saucepan and heat over medium-high heat, stirring occasionally so it doesn’t burn. Meanwhile, whisk together the cornstarch and water until smooth.
When the half-and-half mixture starts bubbling, whisk in the cornstarch slurry and keep whisking until very thick (it should be almost immediate). Remove from the heat and whisk in the rose water and orange blossom water.
Pour the ashta into a bowl or lidded container and top with plastic wrap, pressing the wrap to the surface of the custard (to prevent a skin from forming). You should have about 2 ½ cups of ashta. Cool completely and refrigerate until needed.
To make the syrup: Add the sugar and water to a saucepan and heat over medium-high heat, stirring occasionally. When the mixture starts boiling, add the lemon juice and slightly lower the heat to maintain a gentle boil. Cook for 4 to 5 minutes longer to thicken it slightly.
Remove from the heat and mix in the rose and orange blossom waters. Set aside to cool. This syrup will keep well in an air-tight container in the refrigerator until needed.
To make the atayef pancakes: Combine the dry ingredients in a bowl and then whisk in the milk. Set the mixture aside for about 10 minutes.
Meanwhile, heat a non-stick skillet or griddle over medium to medium-high heat. Add a scant ⅛ cup (about 1 ½ tablespoons) of the batter (which should be slightly thicker than a crepe batter) to the pan to form 3 ½-inch circles. It should spread out on its own. Cook the atayef on one side only. Bubbles will rise to the surface and the top will start to dry out as it cooks (if bubbles do not start to rise almost immediately, your pan isn’t hot enough or the batter is too thick). When the top is dry and the bottom is golden, the pancakes are done. Do NOT flip them. Just set them aside until needed. Continue cooking the pancakes and allow them to cool for a few minutes before assembling.
To assemble: Take each pancake with the uncooked side facing up. Starting at one end press the edges to seal about ⅔ of the way with an opening at the opposite end. It should form a cone shape.
Remove the ashta from the refrigerator and whisk vigorously until smooth (it will be very thick). Fill the ashta into a pastry bag fitted with a medium round tip or into a disposable pastry bag cut at the end. Pipe the ashta into each of the atayef “boats” filling fairly generously.
Immediately dip the exposed ashta of each atayef into crushed pistachios to finish. Serve with the syrup for drizzling. Alternatively, serve with honey.
These are best the day they are made, but leftovers can be stored in the refrigerator for about a day before the texture starts to change significantly.