For the Gingerbread Cookies:
Combine sugar, butter, egg, molasses and vanilla in large bowl. Beat at medium speed, scraping bowl often, until creamy. Reduce speed to low; add all remaining cookie ingredients.
Beat until well mixed. Divide dough in half; wrap in plastic food wrap. Refrigerate until firm (1 to 2 hours).
Heat oven to 375°F. Roll out dough on lightly floured surface, one-half at a time (keeping remaining dough refrigerated), to 1/8-inch thickness. Cut with 4-inch cookie cutter.
Place cookies, 1 inch apart, onto ungreased cookie sheets. Bake for 6 to 9 minutes or until set. Let stand 1 minute on cookie sheets; remove to wire cooling rack. Cool completely. Match up pairs of cookies that are similar.
Decorate half of them with royal icing details to look like gingerbread men. While the icing dries prepare filling.
For the Marshmallow Filling:
Place chocolate chips and butter in a microwave-safe bowl; heat about 1 minute, until just melted. Let stand for 30 minutes, or until slightly stiff.
Heat marshmallow cream in microwave for 10 seconds to soften. Spread marshmallow on a cookie, chocolate on another and sandwich together.