preheat the oven to 350°F and brush oil on the muffin tray.
Sieve oat flour, baking soda, cacao powder, and salt well. Keep aside.
In a bowl combine sugar, water, oil, apple cider vinegar, and chocolate extract. Mix until sugar melts and you get a homogenous mixture.
Combine the dry ingredients to wet and mix well.
Fill muffin cups 2/3 full with batter. Tap it well.
Bake for 15 minutes.
For frosting
In a saucepan add coconut milk, sugar, and oil and bring to heat on a low-medium flame. Add cocoa powder and stir well till you get a smooth consistency.
Frosting the cake
Allow the muffins to cool completely. Remove from the muffin pan and place it in plate covered with cling wrap or foil.
Pour the hot frosting on top and spread on sides.
Refrigerate it for 2 hours or overnight and serve.
Notes
Since oat flour cake will be crumbly remove it carefully. Allow it to cool down completely before you remove it from the pan.
Cover the plate with cling wrap or aluminium foil so that the frosting doesn't stick to the plate and can be easily removed once cooled.