Add the chia seeds, milk, pumpkin puree, maple syrup, almond butter, pumpkin pie spice, and vanilla extract (if using) to a medium bowl. Stir well until everything is fully combined.
Let the mixture sit for about 5 minutes, then stir again to break up any clumps of chia seeds. Divide the mixture evenly between three jars or small containers.
Cover the containers and place them in the refrigerator for at least 3 hours, or overnight for the best texture.
Just before serving, add your favorite toppings. Coconut whipped cream, chopped pecans, granola, a pinch of cinnamon, or an extra drizzle of almond butter all make great choices.
Keep any leftovers in an airtight container in the refrigerator for up to 5 days.