Pour the sesame seeds into a large skillet or pan over medium heat. Toast the seeds for about 3 to 4 minutes, until you can start smelling the aroma of the seeds and see light wisps of smoke coming up from the pan. Turn off the heat.

Carefully transfer the toasted sesame seeds to the bowl of a food processor. Don’t let the seeds cool off before blending. I find the seeds are easier to blend into a paste when they’re still warm. To prevent spilling the seeds everywhere, I recommend transferring the seeds into a bowl or a large Pyrex measuring cup first before pouring the seeds into the food processor. I’ve made too many messes trying to pour the seeds straight from the pan and into the food processor.

Add the powdered sugar to the food processor and blend everything for about 30 seconds. The mixture will look sandy and gray. Next, add the walnut oil, vanilla, and salt. Blend everything again for another 3 minutes or so, scraping down the sides of the bowl about every 30 seconds. The black sesame paste should be similar to the consistency of natural peanut butter that’s been recently stirred–not too runny, and not too thick. Taste the paste and adjust the flavors to your liking, adding more sugar or salt, if necessary.