Whisk the flour, cocoa, baking powder, pie spice and salt together in a large bowl. Whisk the eggs, sugar and melted butter together in a medium bowl until well combined and smooth.
Make a well in the center of the flour mixture and pour in the egg mixture. Gradually whisk to make a thick batter, switching to a rubber spatula when the batter is too thick to whisk.
Preheat a pizzelle iron until a drop of water sizzles on the hot surface, about 10 minutes. Lightly spray the hot surface with cooking spray. Pipe or spoon about a tablespoon of the batter into the center of each cookie imprint. Close the iron and cook until whiffs of steam come from the iron, 30 to 45 seconds. Open the iron and remove the cookies. Transfer to a wire rack to cool and repeat with remaining batter.
For the filling:
Put both chocolates and the butter in a microwave-safe bowl. Cover and microwave in 45 second increments, stirring occasionally, until melted and smooth. Spoon a tablespoon of the filling into the center of half the cookies. Top with another cookie and press to sandwich them together.
When measuring flour, we spoon it into a dry measuring cup and level off the excess. (Scooping directly from the bag compacts the flour, resulting in dry baked goods.)
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