Preheat the oven to 350ºF and line a large baking sheet with parchment paper or a silicone mat.
In a large bowl, stir together the buckwheat flour, coconut sugar, oil, water, vanilla, salt, and baking soda. Then add in the vinegar, which will react with the baking soda to help the cookies rise a bit.
Fold in the chocolate chips, then use a tablespoon to scoop the dough into 12 mounds spaced evenly apart on the lined baking sheet. Flatten each cookie with your hands, as these cookies will only spread slightly. Bake until the edges are firm, about 10 minutes at 350ºF. Let cool at least 10 minutes before serving.
If you'd like to replace some of the oil in this recipe, I've successfully made them using 1/4 cup melted coconut oil with 1/4 cup unsweetened applesauce. In this case, please omit the water in the recipe. The resulting cookies will be softer due to the applesauce, like a cross between a cookie and a muffin top. If you'd like them to be firmer, place them in the fridge and serve cold.