Mix the gelatin with 1/2 cup of the cornstarch and 3/4 cup and 2 tablespoons water and add to the saucepan. Stir constantly until the gelatin has dissolved, then continue to simmer very gently for 20 minutes until thickened.
Mix together the remaining cornstarch and the confectioners’ sugar. Lightly oil a 8 in. (20cm) square baking pan with a depth of 1 1/2-2 in. (4-5cm) and line it with plastic wrap. Lightly dust the plastic wrap with some of the cornstarch mixture, tipping out the excess.
Remove the saucepan from the heat and let cool. Add the rosewater, foodcoloring, and pistachios and pour the mixture into the baking pan. Spread level and let cool for at least4hours or until completely set before cutting into squares and dustingwith the rest of the sugar cornstarch
Recipe from Gifts from the Kitchen: 100 Irresistible Homemade Presents for Every Occasion by Annie Rigg (Kyle Books, 2011). Recipe reprinted with permission.
Chef Thomas Keller, author of Ad Hoc at Home, explains how to season food with salt and vinegar, and why you should temper your food.