Add sugar in a blender or a food processor and pulse for 1-2 minutes or until a powder is formed.
Add the powdered sugar alongside the coconut oil to a bowl and whisk for about 3-4 minutes or until light and fluffy. Make sure to not over-mix it, because the coconut oil will start to melt too much, which is not ideal.
Add milk and vanilla extract and continue whisking.
Sift the flour, cacao powder, salt, and baking powder into the wet ingredients.
Next, mix everything together. It may seem a bit dry at first, but as you continue a cookie dough will form. Finally, add chocolate chips and mix one last time.
Place the cookie dough in the fridge for about 30 minutes so it can firm up. After 30 minutes, if the dough is too soft, let it sit for another 15-20 minutes in the fridge. If it's too hard to form, let it soften at room temperature for about 10-15 minutes.
Pre-heat oven to 180C (356F). Place a piece of parchment paper on a flat baking dish.
Scoop about 2 tablespoon of the dough and form it into a ball. Place on the baking dish and repeat with the rest of the batter. Make sure to leave at least 1 inch of space between each cookie ball to allow spreading.
Bake for 12 minutes. Let them cool for at least 15 minutes before serving.
Save the cookie in a covered jar/container in a dry space for up to 4 days.
Notes
You can use gluten-free flour such as buckwheat flour, but I haven't tried it. However, I think it may work well.
I use Dutch-processed cocoa powder and have not tried this recipe with natural cacao powder.
Instead of chocolate chips, you can use a bar of chocolate and cut it into small bits.
You can also prepare the cookie mixture and leave it in the fridge for up to 2 days before baking. Let it sit at room temperaturefor at least 20 minutes before forming into balls.
If you want to bring your milk to room temperature fast, heat it at medium heat for 1-2 minutes or for a few seconds in a microwave. However, the milk should not be hot.
Make sure you measure all of the ingredients correctly. I found this articlehelpful.