Use a mortar and pestle to mash the garlic and salt together until it forms a paste. If you do not have a mortar and pestle start by finely mincing the garlic. Sprinkle the garlic with salt and then tilt the blade so that it forms a shallow angle with the cutting board. Scrape the knife across the garlic repeatedly, until it forms a paste.
In a large bowl, combine the yogurt, tahini, mint, and lemon. Add the garlic and salt mixture and combine well. Add the cucumber to the yogurt mixture just before serving. Enjoy!