Use 100% pumpkin puree without added sugar or spices; homemade or canned puree works, but do not use pumpkin pie filling., Do not overmix or over-bake the bars, or they can become dry. Keep leftovers in the refrigerator for longer storage and better flavor., Add mix-ins such as chopped walnuts or pecans, dried cranberries, raisins, pumpkin seeds, or dark chocolate chips., For vegan bars, use a flaxseed egg, nondairy cream cheese, and nondairy yogurt. For gluten-free bars, use gluten-free pastry flour, oat flour, or almond flour and check that the baking powder is gluten-free., For dairy-free bars, use nondairy cream cheese and nondairy Greek yogurt. For an almond-flour variation, use just almond flour with keto maple syrup or sugar-free honey. For a protein-powder variation, replace ½ cup (50 g) of flour with vanilla vegan protein powder or vanilla casein., Store cooled frosted or unfrosted bars in an airtight container at room temperature for 1 day or in the refrigerator for up to 4 days. Freeze in a freezer-safe container or individual zipper bags for up to 3 months; reheat in a hot oven for a couple of minutes or in the microwave for 30–40 seconds.