-
Sift the flour and cocoa together.
-
In a large bowl, beat the butter and brown sugar together until light and fluffy.
-
Stir in the flour mixture.
-
Using your hands, form the dough into two logs about 1 inch in diameter.
-
Wrap each log in plastic wrap and refrigerate for approximately 1 hour, or until firm enough to slice.
-
Preheat oven to 350°.
-
Unwrap each log and cut into slices about 1/4 inch thick. Place on ungreased baking sheets.
-
Bake for approximately 8-10 minutes, or until cookies are firm but not browned.
-
Cool for 1 minute on baking sheets, then remove and place on racks. Cool completely.
-
To make filling, place butter in a small saucepan and heat over low heat until melted.
-
Continue to heat, stirring occasionally, until butter just begins to brown.
-
Remove from heat and let cool slightly.
-
Stir powdered sugar and lime juice into melted butter.
-
Spread filling on half the cookies. Top each with an unfrosted cookie and press down gently.