Preheat the oven to 350°F. Line a 12-cup muffin pan with cupcake liners. Set aside.
In a large bowl, sift together the dry ingredients: oat flour, cocoa powder, baking soda and salt.
Add water and milk to a microwave-safe bowl. Heat in 10-second increments until just warm. This will prevent the melted coconut oil from solidifying once mixed with these liquids.
In a medium bowl, whisk together all wet ingredients: water, milk, coconut oil, sugar, maple syrup and extract. Whisk until well incorporated.
Add wet ingredients to dry ingredients. Whisk until just incorporated, making sure no flour patches remain.
Pour batter evenly into prepared muffin pan—fill ¾ of the way for about 12 smaller muffins; fill all the way for 9-10 larger muffins with big, high tops.
Bake for 16-20 minutes. Mine took 18 minutes. Place muffin pan on a cooling rack to cool for 30 minutes. Remove muffins from muffin pan and continue cooling on rack until completely cool, 1-3 hours. Enjoy! Storing instructions below.
*If using homemade oat flour, make sure to sift the flour to remove coarse bits of oats that could create grainy, overly moist muffins without domed tops.Storing Instructions: Store in an airtight container for up to 1 week.Freezer Instructions: These chocolate muffins freeze well. Cool muffins completely, then store in a freezer-friendly container. Keep muffins for 1-2 months.