Preheat pizzelle baker. Over a large bowl, sift to combine flour, cocoa and baking powder.
In a separate large bowl, whisk to combine Sugar In The Raw, Stevia In The Raw and espresso powder. Whisk in eggs then butter and vanilla. Add flour mixture to wet ingredients and mix until just combined.
Add a heaping teaspoon of batter to the bottom grid of the pizzelle baker. Close the iron and cook until the timer light indicates – about 45 seconds. Cool on wire rack and repeat with remaining batter.
To make buttercream begin by dissolving espresso powder into the vanilla extract in a small bowl. Set aside.
In a small saucepan whisk flour and milk over medium-low heat, stirring constantly until it thickens to a paste. Transfer to a bowl to cool completely to room temperature. Stir in vanilla-espresso mixture.
While the mixture cools, using a stand or hand mixer cream the butter, Sugar In The Raw and Stevia In The Raw until light and fluffy – about 5 minutes. Scrape down the sides throughout beating to ensure butter, sugar and stevia combine completely. Add the cooled milk mixture and beat an additional 5 minutes until cohesive.
Arrange half the cookies on your countertop or work surface. Spread buttercream onto cookies and top with remaining half of cookies.