Place the burgers on a bed of greens and top each one with a flew slices of avocado. Drizzle a little tahini dressing over each burger and serve immediately. You may also add your favorite burger toppings such as caramelized onions, sauteed mushrooms, or your favorite burger condiment. I liked it with sliced red onions and tomatoes with the avocado! Any leftover sweet potato mixture can be refrigerated for up to 4 days.