I've never tried these but I found a recipe on the King Arthur Flour blog, so I may.
Pizzelle cioccolatte — chocolate pizzelle — are a delicious variation on the usual almond, anise, and rum-flavored cookies. Snapping crisp yet tender, pizzelle are a must-have at any Italian celebration.
3 large eggs
1 cup sugar
1 teaspoon vanilla
1/2 teaspoon espresso powder
3/8 teaspoon salt
1/4 cup Double-Dutch Dark Cocoa or Dutch-process cocoa
2 teaspoons baking powder
1 2/3 cups King Arthur Unbleached All-Purpose Flour
1/2 cup melted butter
1) Beat together the eggs, sugar, vanilla, espresso powder, and salt till smooth.
2) Add the cocoa and baking powder, again beating till smooth.
3) Add the flour, mixing till well combined. Add the melted butter, again mixing till well combined.
4) Bake pizzelle according to your pizzelle iron instructions. A tablespoon cookie scoop works well for scooping batter onto the iron; a level scoopful of batter is the right size for most standard pizzelle makers.