TO MAKE THE BASBOUSA BASE:
Adjust oven rack to middle position and preheat oven to 180C/ 350F.
In a medium skillet over medium heat, place the full amount of powdered milk and cook, stirring constantly, until toasted and turns deep golden brown in colour; about 10 minutes. Do not rush this process, or be tempted to toast it on high heat, as the powdered milk can scorch easily.

Remove 1/2 cup of the toasted milk powder, and set aside for topping the finished dish later. We'll come back to the remaining 1 cup in a bit, but first...prepare the semolina.
In a large bowl, stir together the semolina and melted ghee together until well combined. Set aside till you prepare the rest of the ingredients; mixture will thicken as it sits.

Back to the toasted milk. Place the remaining 1 cup of the toasted milk powder in a medium bowl and add to it the sugar, canned cream (eshta/ashta), sweetened condensed milk, 3 tablespoons of milk, baking powder and salt. Whisk everything together until well blended.
Pour the toasted milk mixture over the semolina/ghee mixture, and stir with a spatula until well combined.

Take half of the batter, which should weight 445g, and transfer it to a lightly greased 13X9 inch baking dish.* Using a spatula or back of a spoon, spread the batter into an even layer. Set aside.
Into the bowl with the remaining half of the batter, pour the extra 3 tablespoons of milk and stir, until well combined and the batter has thinned in consistency. Transfer the thinned batter to a piping or zipper lock bag with the tip snipped off to make a 1 cm opening. Set aside.

Bake the batter in the dish, for 10 to 12 minutes until the basbousa base starts to set and is no longer wet. Be sure not to bake it all the way through, as it will go back in the oven once more and continue to bake. While the basbousa base is baking, prepare the the cream filling.

TO MAKE THE CREAM FILLING:
In a medium saucepan, off the heat, whisk together the milk, whipping cream, sugar and cornstarch until well combined and the cornstarch has dissolved completely without any visible lumps.
Set the saucepan over medium-high heat and cook, whisking constantly until the mixture forms large bubbles over the surface and reaches a full boil. Continue to cook for about 30 more seconds, until the mixture thickens.

Remove the saucepan from the heat and pour the cream filling over the baked basbousa base and spread into an even layer. Place the dish in the fridge for about 5 minutes to set the cream filling just enough so that the top batter layer doesn't sink into it. It should still remain warm.

TO FINISH:
Pipe the thinned batter (the one waiting in the piping bag) in lines on top of the cream to cover the entire surface. Using a spatula or the back of a spoon, carefully smooth out the lines and cover any areas where the cream is exposed.
Bake again until the surface has fully set and feels done to the touch; 20 to 25 minutes.

Take the dish out of the oven and immediately pour the remaining can of condensed milk all over the surface and smooth out with a spatula to cover the entire surface. Allow the condensed milk to absorb into the basbousa; this can take about 20 minutes. The condensed milk should be mostly absorbed but will leave a thin, opaque film over the surface.
Allow the basbousa to cool to room temperature

Then sift the remaining 1/2 cup (50g) of toasted milk powder evenly over the surface. Use a small spoon to draw diagonal lines into the toasted milk powder layer. Garnish with pistachios around the edges if desired and serve at room temperature or slightly warm.

Taste and texture are at their best the same day it's made, but leftovers will keep well, covered tightly, in the refrigerater for a couple of days. Bring back to room temperature before serving, or lightly warm individual servings in the microwave.