1. Preheat oven to 350 degrees. Line cookie sheets with parchment paper.
2. Beat shortening and sugar until well blended.
3. Add egg and vanilla, beat well.
4. Whisk together dry ingredients and add to sugar mixture alternately with buttermilk, mixes well after each addition.
5. Drop by heaping teaspoons full onto prepared cookie sheets, leaving room between each for expansion.
6. Bake 7 to 8 minutes, allow to cool for a few minutes before transferring to a cooling rack to cool completely.

To prepare filling

1. Butter butter and shortening until creamy, add marshmallow creme and beat until incorporated.
2. Add Peppermint extract, and beat until combined.
3. Gradually add confectioners sugar, and beat until fluffy and well combined.
4. Spread about 1 tablespoon of filling on flat side of cookie and top with a second cookie (flat side touching filling.
5. Fill a bowl with shamrock quins and hold each cookie over the bowl while sprinkling quins onto the edges, gently pressing into filling as necessary.