• Put the black sesame seeds on a dry pan and toast over medium-low heat until fragrant, about 5 minutes or so. Remove from the pan and let them cool down
• To the same pan, add butter and let it melt, then let it cool down
  
• If you have a mortar and pestle, crush the sesame seeds. This helps to release some flavor. If you don't, you can put them in a spice grinder and crush them. They don't have to be crushed completely, some may still be whole, and some partially broken

Prepare the dough:

• Transfer the melted butter to a mixing bowl. Give a tahini a very good stir because it tends to separate. Add tahini to the melted butter and stir to combine.
• Combine all-purpose flour, powdered sugar, salt and black sesame seeds in a large mixing bowl
  
• Add the melted butter and tahini mixture into the bowl.
  
• Use a spatula to combine until you get an evenly combined dough
  
• Place the dough on a piece of parchment paper, large enough for a large baking pan. Shape the dough into about 8 x 8 inches square, about 1/2 an inch thick. I use a bench scraper and my hands to help me shape the dough. If you are really obssessed with getting it perfectly squared corner to corner, you can line a 8 x 8 inch square pan and press the dough onto the pan
  
• Use the tines of the fork to poke the dough all over
  
• Place this in the fridge for at least 1 hour or overnight. If doing overnight, cover the dough with a plastic wrap

Baking:

• When you are ready to bake, preheat the oven to 325 F (160 C) for conventional oven. If using a convection oven, lower the temperature by 20 F/15 C.
• Use a sharp knife to cut the chilled dough into 16 squares and sprinkle with some granulated sugar on top (you can skip if you prefer, but I think it adds a nice texture)
  
• Arrange them on a baking pan lined with parchment paper, about 2 inches apart.
  
• Sprinkle some sugar on top if you choose to
  
• Bake for 30 minutes or until the shortbreads are golden brown

Cool down:

• Let them cool down on the pan completely