Before you begin, have all your ingredients measured and ready. This includes the required tools: a prepared pan, an egg separator, oiled spatulas, a bowl scraper, a mixer, and a candy thermometer.

• Spray an 8" x 8" dish with non-stick cooking spray and dust with flour. Toast pistachios in a preheated oven at 300° F or in a hot skillet.
• Combine sugar, corn syrup, and water in a medium saucepan and cook over medium heat; stir until sugar dissolves. Attach a candy thermometer (affiliate link) on the side of the saucepan. Boil the mixture until it reaches 250° F or the "softball" stage.
• Meanwhile, beat the egg whites in a stand mixer, on high, with a whisk attachment, until stiff peaks form. With the mixer running, add approximately half of the 250° F syrup into the egg whites. Mix on high until stiff, glossy peaks form.
• Boil the remaining syrup until it reaches 290° F or the "hard crack" stage. With the mixer still running, drizzle the remaining syrup into the eggs, in a thin stream. Add cardamom, butter, and vanilla (or rose water). Mix for a few additional minutes, scraping down the sides of the bowl as needed. 
• Replace the whisk attachment with the paddle attachment, and set the speed to low. Add pistachios and mix until combined.
• Transfer the mixture to the prepared baking dish, using an oiled spatula. Allow to cool off before refrigerating. After a few hours, coax the nougat out of the dish and onto a cutting board. Using a large, sharp knife, cut nougat bars into desired portions.
• Wrap nougat bars individually in Saran wrap to keep them from sticking together.