Preheat oven to 350°F (175°C) and line two baking sheets with parchment paper.
In a bowl, whisk together flour, baking soda, and salt.
In a separate bowl, cream together butter and brown sugar until light and fluffy. Mix in molasses, egg, and vanilla.
Gradually fold in dry ingredients until just combined.
Drop spoonfuls of dough onto prepared sheets, spacing about 2 inches apart.
Bake for 8–10 minutes, until golden brown. Let cool completely.
Make the Marshmallow Filling:
In a saucepan over medium heat, melt butter.
Add mini marshmallows and stir until smooth and fully melted. Let cool slightly.
Assemble the Moon Pies:
Spread a generous amount of marshmallow filling on the flat side of one cookie.
Top with another cookie and press gently to form a sandwich.
Chill in the refrigerator for 30 minutes to set the filling.
Coat with Chocolate:
Dip the edges of each Moon Pie into melted chocolate, allowing excess to drip off.
Let chocolate set before serving.
