These are the cookies I made for the cookie exchange at work, and they were pretty tasty, if I do say so myself. They're called "Grandma Sylvia's Salt Butter Cookies" and are from the America's Lost Recipes cookbook.
Now, this name kind of sucks, to be honest. I guess it's named for the fact that you use salted instead of unsalted butter, but they're really more like Rich and Buttery, Whiskey-Tinged, Chocolate-Filled Sandwich Cookies of Absolute Fabulousness. (Or, as my co-workers immediately named them "the little hamburgers".)
Not "Salt Butter Cookies". Lame. But whatever.
Here's the recipe:
2 egg yolks
1 teaspoon vanilla extract
1 teaspoon whiskey
1 cup (2 sticks) salted butter, room temperature
2/3 cup granulated sugar
2 1/4 cups all-purpose flour
1 ounce unsweetened chocolate, broken into pieces
1/4 cup boiling water (from the kettle)
2 cups confectioners' sugar
1.) Preheat oven to 350 degrees and line a cookie sheet with parchment paper.
2.) In a small bowl, whisk together the egg yolks, vanilla and whiskey. Set aside.
3.) In a mixing bowl, cream the butter and sugar together until fluffy.
4.) Beat in the yolk mixture.
5.) Add the flour and beat until incorporated.
6.) Shape the dough into 3/4-inch balls* and place 1 inch apart on the cookie sheet.
7.) Bake until lightly browned around the edges, 10 to 12 minutes.
8.) Cool on the baking sheet for 2 minutes, then transfer to a wire rack to cool completely, about 1 hour.
9.) When the cookies are cool, pour the boiling water over the chocolate pieces, stirring until completely smooth.
10.) Stir in the confectioners' sugar until smooth.
11.) Spread 1 teaspoon of filling on one cookie and top with another cookie, pressing them together. Repeat with remaining cookies.
12.) Let the filling set until hardened, about 20 minutes, before serving.
These will keep in an airtight container for up to three days. They're also astonishingly good dipped in tea.
*Make the balls smaller than you think they should be. If you make them too big, the little domes will seem fine on the cookie sheet, but will be kind of a mouthful when they're stuffed with chocolate and stacked on top of each other.