Preheat the oven to 350°F (175°C).

In a mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until smooth.

Add the vanilla extract and eggs, and mix until well combined.

In another bowl, whisk together the flour, baking soda, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Fold in the chocolate chips.

Drop tablespoon-sized balls of cookie dough onto a baking sheet lined with parchment paper.

Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden.

Remove from the oven and let cool on the baking sheet for a few minutes before transferring to a wire rack.

In a mixing bowl, combine the powdered sugar, softened butter, and milk.

Mix until smooth and creamy, then add blue food coloring until desired color is achieved.

Once the cookies are completely cooled, spread a generous amount of blue frosting on top of each cookie.

Serve and enjoy your Cookie Monster Cookies!