How to Make It
Preheat the oven to 350º and line 2 baking sheets with parchment paper. In a small bowl, whisk the flour with the baking powder, baking soda and salt.
In the bowl of a standing electric mixer fitted with the paddle, cream the butter with the peanut butter, sugar and molasses at medium-high speed until light and fluffy, about 2 minutes. Add the egg and vanilla and beat at low speed to combine. Add the flour mixture and beat at low speed to combine.
Divide the dough into 2 equal pieces and wrap in plastic wrap. Refrigerate until firm, about 15 minutes.
Roll out each piece of chilled dough to about 1/4 inch thick. Using a 2-inch round cutter, stamp out rounds and arrange them 1/2 inch apart on the prepared baking sheets; roll and stamp out the dough scraps. Freeze the rounds for about 15 minutes.
Bake the rounds for about 10 minutes, shifting the pans halfway through baking, until the cookies are firm around the edges. Let the cookies cool slightly on the baking sheets, then transfer to wire racks to cool completely.
Spoon about 1 tablespoon marshmallow creme onto 30 of the flat sides of the cookies, then gently sandwich with the remaining cookies. Freeze until firm, about 30 minutes.
Meanwhile, place two-thirds of the chocolate into a bowl over a deep skillet of boiling water. Melt the chocolate to 115º and remove from the heat. Stir in the remaining one-third of the chocolate and let stand for 5 minutes; stir to combine. Let the chocolate cool to 90º.
Submerge each cookie sandwich in the melted chocolate and turn to coat, shaking off any excess; reheat the chocolate to 90º as needed. Transfer the moon pies to parchment paper and let set for at least 1 hour before serving.