In a large mixing bowl, beat butter with an electric mixer on medium to high speed for 30 seconds. Add sugar and salt. Beat until combined, scraping sides of bowl occasionally. Beat in egg and vanilla. Beat in as much flour as you can with the mixer. Stir in any remaining flour. Cover; chill dough about 1 hour or until dough is easy to handle.

Preheat oven to 375 degrees F. Shape dough into 1-inch balls. Place 2 inches apart on ungreased cookie sheets. Bake in the preheated oven for 8 to 10 minutes or until cookies are lightly browned around the edges. Remove from oven and make a small indent in the center of each cookie using the bowl of a small measuring spoon or melon baller. Transfer cookies to a wire rack and let cool.

Just before serving, use a decorating bag fitted with a star or round tip to pipe Peppermint Filling into the center of each cookie. Sprinkle filling with crushed candy canes. Makes about 3 dozen cookies.

In a medium mixing bowl, beat 1/4 cup softened butter with an electric mixer on medium to high speed for 30 seconds. Beat in 1/4 teaspoon peppermint extract. Gradually beat in 1-1/2 cups powdered sugar. Beat in enough milk (2 to 3 teaspoons) to make a filling of piping consistency.

Prepare as above. Place a milk chocolate kiss on top of filling in the center of each cookie, pressing in slightly.

Layer unfilled cookies between waxed paper in an airtight container; cover. Store at room temperature for up to 3 days or freeze for up to 3 months. Fill before serving.