Combine the butter, sugar, and tahini in the stand mixer with the paddle attachment. Mix on medium speed until smooth, around 4 minutes.
Add the flour and salt and mix on low speed until the dough is uniform and smooth.
Transfer the dough to a clean, lightly floured work surface and divide the dough in half. Roll each half into a roll or shape into a rectangle if the dough is proving difficult to work with.
Roll each half of the dough in the sesame seeds to coat the surface completely.
Wrap the dough tightly in cling film and place in the fridge to chill for at least four hours.
Preheat the oven to 300 degrees Fahrenheit and line two baking sheets with parchment paper.
Slice the logs into 1/4" thick slices and place on the prepared baking sheets.
Bake until firm around the edges and not colored.
Let the cookies cool on the baking trays. Store in an airtight container and consume within three days