Put parchment paper on a sizable baking sheet and preheat the oven to 325.
To prepare the pies, mix the almond flour, coconut flour, granular sweetener, baking powder, and cocoa powder in a medium bowl. Place aside.
Cream the butter, heavy cream, almond milk, eggs, vanilla extract, and stevia in a separate bowl.
Mix dry components with the wet ones.
Using a 1" cookie scoop, drop the batter onto the parchment-lined baking sheet, leaving 2" between scoops.
Bake for 18 to 20 minutes at 325 to ensure complete cooking.
To make the buttercream, combine the butter, stevia, powdered sweetener, and salt in a mixing bowl and beat until smooth.
Don't overbeat the icing or the heavy cream will turn to butter; instead, add the heavy cream and beat until it is light and fluffy.
Two whoopie pies should be spread with buttercream after cooling. depending on the amount of the cookie scoop used, yields 12–18 keto whoopie pies.