Preheat the oven to 350ºF and line a baking sheet with parchment paper or a silicone mat. In a large bowl, stir together the ground chia seeds and water. This is your "chia egg." (You can use a real egg if you'd rather skip this.)
Add the almond butter to the chia seed mixture, along with the coconut sugar, cocoa, salt, baking soda, peppermint extract, and vinegar. Stir well until a thick and uniform mixture is created. Gently fold in the chocolate chips, if using, then drop the dough by rounded tablespoonfuls onto the lined baking sheet. Use your hands to gently flatten each cookie.
If you'd like to add the crushed candy cane pieces to the top, sprinkle them on generously before baking. They will melt in the oven and then re-harden when cooled for a crunchy peppermint-flavored topping.
Bake the cookies at 350ºF until the cookies have slightly spread and the tops look dry, about 9 to 12 minutes. The cookies will still be very soft to the touch, so it's important that you let them cool on the pan for at least 20 minutes before trying to move them to a wire cooling rack. Allow the cookies to cool completely before serving.
These cookies can be stored uncovered at room temperature for up to 3 days, but for best shelf life keep them in the fridge or freezer. They should last up to two weeks in the fridge, and up to 3 months in the freezer. If you don't eat them all before then!