Preheat oven to 350°F. Lightly grease two baking sheets.

For cookies: In a large bowl, sift together the flour, baking soda, and salt.

Put the butter, brown sugar, and 2 tablespoons of water into a large saucepan over low heat and stir as the butter melts. Add the chocolate chips and stir as the chocolate melts. Remove the pan from the heat and set aside to cool slightly. Add the eggs to the chocolate mixture and, with an electric mixer, beat to blend. Add the flour mixture and stir to combine.

Drop by heaping teaspoonfuls onto the prepared baking sheets. Bake for 8 to 10 minutes, or until the edges are dry but the cookies are still soft in the middle. Transfer the cookies to a rack to cool completely.

For filling: Using a stand or hand electric mixer, combine all of the filling ingredients and mix until smooth.

Spread 1 teaspoon of filling on one cookie, then top with another cookie.