Preheat the oven to 350ºF. In a large bowl, mix together the softened butter and coconut sugar until they look relatively creamy.
Add in the egg and vanilla and mix again. Then add in the dry ingredients, including the oat flour, baking soda, and salt. Mix well, until the batter looks thick and uniform. Fold in the chocolate chips.
Use a 1-ounce cookie scoop, or heaping tablespoon, to scoop the dough and drop it onto a large baking sheet lined with parchment paper. Arrange the mounds of dough about 2 inches apart from each other, to allow for spreading as they bake. Bake at 350ºF for 8 to 11 minutes, depending on how crispy you like your cookies.
Let the cookies cool on the pan for at least 20 minutes; they will be very fragile when hot from the oven. These cookies can be served warm or at room temperature after that, but they will soften and start to crumble if you store them in a bag at room temperature overnight. For a firmer texture, store them in the fridge for up to a week.
Video
Notes
Nutrition information is for 1 of 24 cookies. This will vary depending on how many cookies you get from this batch, so it's just an estimate and not a guarantee.Measuring Oat Flour: I use the "scoop and swipe" method to measure oat flour, which means I scoop the measuring cup into the bag of flour and level off the excess with the back of a knife. This means the cups I use are tightly packed compared to spooning the flour into the cup. For the best results, I recommend using a food scale to make sure you use the correct amount of oat flour. (Using too little will result in cookies that spread out on the pan.)Gluten-Free Note: Oats are naturally gluten-free, but may be contaminated during processing. Be sure to look for a "certified gluten-free" label on the package if you need a gluten-free cookie.Make them Vegan: Use 1 flax egg (1 T ground flax + 3 T water) to replace the egg, and vegan butter (I tested with Miyoko's brand) to replace the butter.