Creating Peppermint Chocolate Cookie Sandwiches can be easy if you follow these simple steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper.
2. Cream Butter and Sugars: In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
3. Add Eggs and Vanilla: Beat in the eggs one at a time, then stir in the vanilla extract.
4. Mix Dry Ingredients: In another bowl, whisk together the flour, cocoa powder, baking soda, and salt.
5. Combine Mixtures: Gradually add the dry ingredients to the wet ingredients, mixing until fully combined. Fold in the chocolate chips.
6. Scoop the Dough: Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheets, spacing them about 2 inches apart.
7. Bake: Bake in the preheated oven for 10-12 minutes until the edges are set but the centers are still soft. Remove from the oven and allow to cool on the baking sheets for a few minutes before transferring to wire racks.
8. Make the Filling: In a medium bowl, beat together the powdered sugar, milk, and peppermint extract until smooth and creamy.
9. Assemble the Sandwiches: Once the cookies are completely cool, spread a generous amount of filling on the bottom side of half the cookies. Top with the remaining cookies to create sandwiches.
10. Garnish (Optional): If desired, sprinkle crushed peppermint candies on the filling for added crunch and flavor.

These steps will guide you in creating these incredible cookie sandwiches effortlessly.