Preheat oven to 350F. Spray a whoopie pie pan (or muffin top pan) with non-stick spray and set aside.
In a large bowl, beat together ½ cup butter and coconut sugar on high speed until light and fluffy.
Add in egg and mix on low speed until well incorporated.
In a separate bowl, sift together oat flour, cacao powder, baking soda, baking powder, and salt.
Add ½ of the dry mix to the bowl of butter mixture. Mix until well combined.
Next, mix in almond milk and peppermint extract until well combined.
Lastly, add remainder of dry mix and mix just until incorporated.
Evenly distribute batter among the 12 whoopie pie molds, filling each about 2/3 full.
Bake in the oven for 10-12 minutes (you’ll repeat this step again – making 24 half pies). Let cool on wire rack while you make the icing.
For the icing, beat all ingredients on high speed in a large mixing bowl until smooth and creamy. If the icing is too runny, place in the fridge until it firms up a bit (about 5-10 minutes).
When icing is ready, spread about 2 tablespoons of icing on one-half of a whoopie pie. Repeat until icing is on 12 pies.
Top each pie with the other half and enjoy!