Ingredients
Cooking spray
16 ounces tahini or sesame paste about 1 3/4 cups
1/2 cup shelled pistachios, optional
1/2 cup water
1 pound sugar, about 2 1/4 cups
Lightly spray an 8 1/2-by-4 1/2-inch loaf pan with cooking spray and line it with parchment paper, leaving some overhang on two opposite sides.
Put the tahini in a large, heatproof bowl. Add the pistachios, if using; stir and set aside.
Put water in a medium saucepan and bring it to a boil over medium-high heat. Add the sugar and stir until dissolved.
Attach a candy thermometer to the pot and heat over medium-high heat until the syrup reaches 250 F (it should be golden, and not dark), 5 to 8 minutes. Dip a pastry brush in water and brush over the sides of the pan to wash away any sugar crystals as the syrup heats.
Gradually add the hot syrup to the tahini while stirring constantly. Continue to stir for about 20 to 40 seconds, or just until the mixture thickens enough to pull away from the sides of the bowl, then quickly turn it into the prepared loaf pan. Top with more pistachios, if desired.
Let the helva cool. Remove it from the loaf pan using the parchment paper overhang as handles. Remove and discard the parchment. Cut into squares and serve. Garnish each serving with additional chopped nuts, if desired.
