In a frying pan, toast pistachios until fragrant over medium heat. Set aside to cool. In the meantime, combine sugar and water in a saucepan over medium heat, stirring to dissolve the sugar. Allow to simmer until the mixture starts to bubble, approx. 7 min.
Add tahini and salt to a bowl and beat with a hand mixer with beaters on medium speed. Carefully pour bubbling sugar mixture into the tahini. Mix until it’s fully incorporated and fudgy, approx. 20 seconds. Do not overmix!
Transfer mixture immediately into a parchment paper-lined baking pan. Cover with toasted pistachios and let cool completely, approx 2 hrs. Cut into squares. Enjoy!