Heat oven to 350°. Have 2
whoopie pie pans ready. In a medium bowl, whisk flour,
cocoa powder, baking soda and salt.
In a large bowl, beat butter with an
electric mixer for 30 seconds, until creamy.
Beat in brown sugar for 1 minute, until
fluffy, and beat in egg for 1 minute. Beat in
vanilla. On low speed, beat in flour mixture,
alternating with buttermilk, beginning and
ending with flour. Divide evenly between
pans, spreading batter slightly until level.
Bake at 350° for 11 to 13 minutes or until
dry to the touch. Remove from pans to a
wire rack to cool.
In a medium bowl, beat butter
and cream cheese until smooth. Fold
in marshmallow crème and tint with food
coloring to desired color. Spread 1 to
2 tbsp of the filling onto flat side of a
cookie. Sandwich with a second cookie.
Repeat; refrigerate pies in an airtight
container up to 4 days. Let stand at room
temperature before serving.