• 1 1/4 cups all-purpose flour
• 1/2 tsp coarse salt
• 1/2 cup (1 stick) unsalted butter, room temperature
• 2/3 cup granulated sugar
• 1 tsp vanilla
• 1 large egg
• 4 oz semisweet chocolate, coarsely chopped
• 3/4 cup confectioners’ sugar
• 1/4 tsp pure peppermint extract 

1. In a small bowl, whisk together flour and salt. In a medium bowl, using an electric mixture, beat butter and granulated sugar on high, scraping down bowl as needed, until light and fluffy. Add vanilla and egg and beat to combine. With mixer on low, gradually add flour mixture and beat until just combined.

2. Transfer dough to a quart-size zip-top bag; with scissors, snip a 3/4-inch hole in one corner (or use a pastry bag with a plain tip). Pipe 54 cookies (3/4 by 2 inches), 1/2 inch apart, onto two parchment-lined baking sheets. Chill until firm, 20 minutes.

3. Preheat oven to 325 degrees, with racks in the upper and lower thirds. Bake until cookies are light golden at edges, about 15 minutes, rotating sheets halfway through. Transfer immediately to wire racks and let cool.

5. Melt chocolate in a glass bowl in the microwave, about 1 1/2 minutes stirring every 30 seconds. In another bowl whisk together confectioners’ sugar, peppermint extract and 4 tsp water.

6. With a table knife or small offset spatula, spread chocolate on flat side of half the cookies and mint glaze on the other half. Sandwich cookie halves together. If your chocolate doesn't set, put it in the refrigerator until it hardens. Cookies can be stored in an air-tight container up to 5 days

Source: http://www.handletheheat.com/2010/10/homemade-milano-cookies.html