Mix tahini and honey together until smooth.
Add powdered milk, vanilla, and salt, stirring well with a spatula until the mixture becomes stiff. *Optional* stir in the chopped pistachios.
Press the mixture onto a piece of parchment paper. Using your hands, shape it into a 5x7-inch rectangle (13x18 cm) or any shape you desire.
Refrigerate for 2-3 hours until set.
Cut into small cubes and store in the refrigerator for up to four weeks. It is also delicious straight out of the freezer!