Toast black sesame in a pan over medium heat until fragrant. Shake the pan back and forth being careful not to burn them. Allow to fully cool. Then in a food processor, blend sesame and honey until you get a smooth paste. Feel free to use more or less honey, you can even substitute some honey for coconut milk for a looser creamier paste.
Make the pastry by mixing together the dry ingredients. Then using your hands or a pastry blender, quickly incorporate the cubed butter. It should resemble fine to medium crumbs. Drizzle in cold water and distribute evenly. Knead in bowl until it comes together. Divide in half, wrap each in plastic wrap, and refrigerate for approx. 30min.
On a floured surface roll out the dough. Then using a knife, cut out six roughly 7cm x 10.5cm rectangles and carefully place them on a parchment-lined sheet. Spread around 2tsp of black sesame paste in the center, leaving a 1cm border. Roll out the rest of the dough to cover your Pop-tarts. Use a fork to seal the edges. Then poke 6 holes on top to allow for the steam to escape.
Bake at 175C for approx. 20min or until edges are light golden brown. Allow to cool on the baking sheet.
To make the glaze, mix together powdered sugar, sesame paste, and a few splashes of milk to loosen it up. The glaze should be thick and run very slowly. Glaze your pastries and sprinkle with black sesame.