In a saucepan, heat butter, sugar and water. Add chocolate chips and stir until partially melted. Remove from heat and stir until all chips are melted. Set aside to cool for 10 minutes.
Meanwhile, beat eggs at high speed. Add flour and baking soda and beat until blended. Add chocolate mixture and blend well. Chill dough for 1 hour.
Line baking sheets with parchment. Roll dough into 1" diameter balls. Bake at 350° for 10-12 minutes.
Place unwrapped mint on top of each warm cookies as soon as you remove them from the oven. After the mints have softened, spread the mint over the cookies with a spoon. Let the chocolate set at room temperature.