Preheat the oven to 350ºF / 175ºC degrees.

Place the butter, sugar, chocolate chips, and water into a saucepan over low heat. Stir until the chocolate has melted and the mixture is smooth.

Allow to cool.

Once cooled, beat in the eggs and vanilla extract.

In a bowl, combine the flour, baking soda, and salt, then add this into the chocolate mixture.

Using a small ice cream scoop, drop spoonfuls of the mixture onto an ungreased baking sheet, leaving a 2-inch gap between each one to allow for rising and spreading during the baking process.

Bake for around 10–12 minutes until firm. Allow to cool on the tray for a few minutes, then remove to a wire rack to cool completely.

In a large mixing bowl, place the powdered sugar, butter, milk, and peppermint extract. Mix until smooth, then add in the food coloring a drop at a time until you have the desired color.

Place the filling into a piping bag and pipe onto the underside of one cookie, then top with another to create sandwiches.