Whether you grind your own sesame seeds to make tahini or buy it in a jar, you eventually have to mix it. Over time, the oil in tahini separates and rises, leaving the solids underneath dry and packed solid. You have to homogenize the tahini to use it, which takes a lot of elbow grease or a little help from a food processor or stick blender. If you have a small jar of tahini, you might be able to mix it by hand, but if you have more than a cup or two, you save time with a machine.
Small Container or Jar
Turn the container of tahini on its side and let it sit for 15 minutes.
Turn the tahini right side up and take the lid off.
Insert a butter knife between the paste and the side of the container where the oil collected.
Work the knife through the tahini paste outward from the point where the oil collected when it was on its side. Continue stirring the tahini paste until homogenized, which occurs when the solids and oil are thoroughly combined and smooth. If you're having trouble mixing with a butter knife, transfer the tahini to a food processor and pulse it until homogenized. Store the tahini jar upside down on a saucer.
Open the container and place an immersion blender on top of the tahini paste. Turn the immersion blender on and press it down through the paste and back up several times to mix the tahini. If you don't have an immersion blender or worry that the container is so full the immersion blender will make a mess, pour the oil off the tahini and into a food processor or stand mixer.
Scrape the tahini from the container into the food processor or stand mixer using a spoon and a spatula. Run hot water over the sides of the container to help loosen the tahini if you can't dislodge it.
Pulse the tahini paste in the food processor or mix it on low using the paddle attachment of the stand mixer until homogenized. Return the tahini to the original container and store it upside down on a saucer.