Combine flour, cocoa, baking soda and salt in bowl; set aside.
Beat sugar and 1 cup softened butter in bowl at medium speed until creamy. Add egg and vanilla, beating until well mixed. Gradually add flour mixture, beating at low speed after each addition.
Divide dough in half; wrap each in plastic food wrap. Refrigerate at least 2 hours or until firm.
Heat oven to 375°F. Line cookie sheets with parchment paper; set aside.
Roll chilled dough on lightly floured surface to 1/8- to 1/4-inch thickness. Cut dough into 2 1/2-inch wide strips. Working with 1 strip at a time, cut cup shapes that are 3 inches on the top edge and 1 1/2 inches on bottom edge (see diagram). Save scraps.
Place onto prepared cookie sheets. For handle, use dough scraps to cut half circles. Attach to sides of cups, pressing slightly.
Bake 8-10 minutes or until cookies are set. Remove sheet of parchment to cooling rack. Cool completely.
Beat powdered sugar and 1/2 cup butter in bowl at medium speed until creamy. Add almond flavoring and enough half & half for desired consistency. Place 1 cup frosting into resealable plastic food bag; snip off small corner of bag.
Decorate cups by squeezing frosting bag to outline cup handle and curve at top of cup. Spread frosting onto cookie below curved line. Add 3 miniature marshmallows above the curve, using a dot of frosting to attach each marshmallow. Add additional decorations, as desired.