Combine the butter, brown sugar, and water in a large microwave-safe bowl. Microwave in 30 second bursts, stirring between each burst, until the butter and chocolate are completely melted and the mixture is smooth.

Add the eggs and vanilla to the chocolate mixture and beat well using an electric hand mixer or stand mixer.

Mix in the flour, baking soda, and salt until combined and no streaks of flour remain. Cover dough with plastic wrap and refrigerate for at least 1 hour.

Roll the dough into small balls, roughly the size of walnuts, and space about 2-inches apart on the prepared baking sheets. Bake for 8-10 minutes until set around the edges and cracked on top, but be careful not to overbake.

Remove the cookies from the oven and wait for 1 minute before topping each cookie with an unwrapped Andes mint. The chocolate mints will melt in about 60 seconds from the residual heat in the cookies. As the mints melt, use a butterknife to spread the chocolate around the top of each cookie.

Let the cookies cool completely. As they cool, the Andes Mints will set up again forming a chocolate-mint coating on top of each cookie.