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!