Cooking spray or vegetable oil
For the sugar syrup
3 cups (575 g) granulated sugar
1/2 cup (175 g) honey
1/2 cup (120 g) water
Pinch of cream of tartar
For the cornstarch mixture
1 cup (150 g) cornstarch
1 cup (130 g) confectioners' sugar (icing sugar)
2 1/2 cups (600 g) water
1 teaspoon (3 g) cream of tartar
For the flavoring
2 1/2 teaspoons (12 g) rosewater
2 cups (300 g) shelled roasted unsalted pistachios
2 or 3 drops red food coloring (optional)
For cutting and dredging
About 1/4 cup confectioners' sugar, for dusting the cutting board (icing sugar)
1/2 cup cornstarch sifted together with 1 cup confectioners' sugar
Small (9" x 13") rimmed baking sheet
Heatproof spatula or wooden spoon
Large cutting board
Generously coat the baking sheet with cooking spray, and set it aside.
Make the sugar syrup: Combine the sugar, honey, water, and cream of tartar in a medium-size saucepan, and mix with the heatproof spatula to combine. Bring the mixture to a boil over high heat, and insert the sugar thermometer. Reduce the heat to medium-high and cook, without stirring, until the temperature reaches 260°F/127°C, about 15 minutes.
Meanwhile (keeping an eye on the sugar syrup), make the cornstarch mixture: In a large saucepan, whisk together the cornstarch, confectioners' sugar, water, and cream of tartar to combine. Once the sugar syrup reaches 250°F/121°C, place the cornstarch mixture over medium heat and cook, stirring constantly with the whisk; it will thicken and boil quickly, 2 to 3 minutes. Turn off the heat, but leave the mixture on the hot burner; stir well a few times with a whisk, and set aside.
At this point, the sugar syrup should be close to 260°F/127°C; when it reaches that temperature, remove it from the heat and carefully pour it into the cornstarch mixture. Stir well with the whisk to combine. Bring everything to a low boil over medium heat. Then reduce the heat to low and cook at a low simmer, stirring frequently with the spatula, until the mixture is thick and gluey and a light golden color, 30 to 45 minutes. Don't turn your back on it! You need to make sure to scrape the bottom of the pan with the spatula every few minutes to prevent scorching and lumps.
Remove the pan from the heat and add the flavorings: stir in the rosewater, pistachios, and food coloring (if using).
Wearing oven mitts, immediately pour the candy into the prepared baking sheet. Place a piece of plastic wrap directly on the surface of the candy to prevent it from forming a skin as it cools. Allow it to cool until it has set and is firm and cool to the touch, 6 to 8 hours.
Gently peel off the plastic wrap. Dust the cutting board with the confectioners' sugar. Run the tip of a paring knife between the candy and the sheet, and gently turn the candy out onto the prepared board.
Place the cornstarch mixture in a medium-size bowl. Generously coat a sharp chef's knife with cooking spray, and use a gentle slicing motion to cut the candy into 1-inch squares. Dredge the pieces in the cornstarch mixture until well coated.
Store the Turkish delights, layered with wax paper, in an airtight container at cool room temperature for up to 1 month.