Avoid chilling dough for spritz like these delicious chocolate-peppermint cookies. You want the dough to be soft enough to press out.
Preheat oven to 375°F. In a large bowl beat butter with a mixer on medium to high 30 seconds. Add sugar, baking powder, and baking soda. Beat until combined, scraping bowl as needed. Beat in yogurt, egg, vanilla, and peppermint extract. Beat in as much of the flour as you can with the mixer. Stir in any remaining flour.
Fit a cookie press with a rosette plate. Force unchilled dough through cookie press 1 inch apart onto ungreased cookie sheets. If desired, sprinkle half of the cookies with red sprinkles or peppermint candies. Bake 8 to 10 minutes or until edges are firm but not brown. Remove; cool on wire racks.
Spread bottoms of half of the cookies with Chocolate-Peppermint Filling. Top with bottoms of remaining cookies.
In a large bowl beat butter with a mixer on medium 30 seconds. Beat in 1 cup powdered sugar and cocoa powder. Beat in 3 Tbsp. of the milk, the vanilla, and peppermint extract until combined. Beat in the remaining 1 1/2 cups powdered sugar until fluffy. If necessary, beat in 1 to 2 Tbsp. additional milk to make filling spreadable.