In a medium 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 as much of the flour as you can with the mixer. Stir in any remaining flour. Divide the dough in half.
Add the 1/3 cup miniature semisweet chocolate pieces, mint extract, and a few drops green food coloring to one dough portion; stir until combined. Add the vanilla to the remaining dough portion; stir until combined.
Divide each portion in half. Shape each dough half into an 8-inch roll. Wrap rolls in plastic wrap. Chill rolls about 2 hours or until very firm.
Preheat oven to 375°F. Line cookie sheets with parchment paper. Using a serrated knife, cut dough rolls crosswise into 1/4-inch-thick slices. For each wreath, alternate four slices of green dough and four slices white dough to form a circle, slightly overlapping slices. Leave a 1-inch circle in the middle. Space cookies 2 inches apart on the prepared cookie sheets.
Bake for 10 to 12 minutes or until edges are firm but not brown. Cool on cookie sheet for 5 minutes. Transfer to a wire rack and let cool.
If desired, in a small saucepan heat and stir semisweet chocolate pieces and shortening over low heat until melted and smooth. Transfer chocolate to a small resealable plastic bag. Snip off a small corner of the bag. Pipe a bow onto each cookie wreath. Let stand until set.
Layer cookies between sheets of waxed paper in an airtight container; cover. Store at room temperature for up to 3 days or freeze for up to 3 months.
(7 g saturated fat,
0 g polyunsaturated fat,
3 g monounsaturated fat),
20 mg cholesterol,
81 mg sodium,
19 g carbohydrates,
1 g fiber,
10 g sugar,
2 g protein.