Recipe courtesy of Judy's Kitchen (http://judyskitchen.blogspot. com
Source:  Bon Appetit Magazine, December 2009 issue
Rating:  10 out of 10
2 cups unbleached all-purpose flour
1/4 tsp. fine sea salt
1 cup (2 sticks) unsalted butter, room temperature
 1 cup sugar
1 tsp. pure vanilla extract
1 large egg yolk
6 oz. bittersweet or semisweet chocolate, chopped
1/2 cup finely chopped red-and-white-striped hard peppermint candies or candy canes (about 3 oz.)
2 oz. high-quality white chocolate (such as Lindt or Perugina)

Preheat oven to 350F.  Spray a 13x9x2-inch metal baking pan* with nonstick spray.  Line bottom of pan with long strip of 9”-wide parchment paper, leaving overhang on both short sides of pan.  Whisk flour and salt in medium bowl.  Using electric mixer**, beat butter in large bowl until creamy, about 2 minutes.  Gradually beat in sugar.  Continue beating until mixture is light and fluffy, stopping occasionally to scrape  down sides of bowl, about 3 minutes.  Beat in vanilla, then egg yolk.  Gradually add flour mixture, beating on low speed just to blend.

Drop dough by tablespoonfuls onto prepared baking pan, spacing evenly.  Using moistened fingertips, press dough to form even layer over bottom of pan.  Pierce dough all over with fork.

Bake cookie base until light golden brown and slightly puffed and edges begin to come away from sides of pan, about 30 minutes***.  Place pan on rack; immediately sprinkle bittersweet chocolate over.  Let stand until chocolate softens, about 3 minutes.  Using small offset spatula, spread bittersweet chocolate over top of cookie in thin even layer.  Immediately sprinkle chopped peppermint candies over.

Stir  white chocolate in medium metal bowl set over saucepan of simmering (not boiling) water until melted and smooth.  Remove from over water.  Using fork, drizzle white chocolate all over cookies.  Chill until white chocolate is set, about 30 minutes****.

Using paper overhang as aid, lift cookie from pan and transfer to work surface.  Using large knife,  cut cookie into irregular pieces.  (Can be made 1 week ahead.  Store in refrigerator in airtight containers between layers of waxed paper or parchment paper. ) Yield will depend on how the cookies are cut. 

VARIATION:  Sprinkle the melted dark chocolate with chopped peanut brittle or peanut butter cups instead of the peppermint candies.

NOTES:  *I used a brownie pan.
**I used my heavy-duty Kitchen Aid stand mixer, which I believe overbeat the dough.  It puffed up and wrinkled in the pan, then deflated; but the shortbread was still fabulous.  Next time, I will beat the mixture less and use 325F as my oven temperature.
***My cookie was done in 20 minutes, leading me to believe the oven temperature was too high.  My pan was dark and coated and I think 325F would have worked better.
****After one hour, chocolate was still soft.  I had to put the cookie in the fridge to get it to set.