Preheat oven to 350F. Line baking sheets with parchment paper.

In a heat proof mixing bowl, melt chocolate and butter in a double boiler over low heat or in the microwave at 10-second increments on medium power, stirring constantly, until it is melted. Allow the mixture to cool to room temperature.

In a large mixing bowl, whisk together sugar, eggs, vanilla, and the chocolate mixture. Whisk in flour, cocoa powder, baking powder, and salt, and stir until well combined.

Drop dough by heaping tablespoons (spacing them 2-inches apart) on prepared baking sheets. Bake for 10 to 12 minutes, or until the tops are no longer shiny and toothpick inserted in center comes out clean. Transfer cakes to wire racks to cool completely.

To make the cream filling, place butter in the bowl of a mixer fitted with the paddle attachment and beat on medium speed until smooth, about 1 minute. Reduce speed to low and gradually beat in confectioners’ sugar until incorporated. Beat in vanilla and marshmallow creme until light and fluffy.

To assemble, spread a heaping tablespoon of filling on flat side of cookie and top with another cookie. Repeat with remaining cookies.