Preheat oven to 350 degrees. Line your cookie sheets with parchment paper.
In a large bowl, cream together the butter, brown sugar and white sugar until light and fluffy.
Add eggs one at a time, beating well with each addition. Add the salt and vanilla and mix until combined.
In another bowl, combine the flour, cocoa and baking soda and gradually add to the creamed mixture.
Fold in chocolate chips.
Use a medium cookie scoop to place dough onto the prepared cookie sheet. I can fit 12 on a half sheet baking pan. Bake for 7 minutes until fluffy but still soft. Do not overbake!
Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.
Frosting
While the cookies are baking, start the frosting. Beat 1 cup of softened butter in a stand mixer with a paddle attachment (or hand mixer) until light and fluffy, about a minute.
Add the powdered sugar, salt, peppermint extract, vanilla extract, and 4 T. heavy cream, and mix on low speed until incorporated. Increase the speed, and beat until creamy and fluffy, adding more heavy cream as needed to get the right consistency. If it's too thin, add a bit more powdered sugar.
Note - You can adjust the peppermint extract to your taste. Start with a little--you can always add more. You want to avoid the toothpaste taste!
Unwrap the candy canes or peppermint candies, place in a plastic quart bag, and use a rolling pin to crush into pieces. You can also use a food processor if you have one.
Add a handful of the peppermint bits into the frosting and mix with a wooden spoon. Amounts are to your preference! Make sure you have enough reserved to sprinkle on top of the finished cookies.
Layering the cookies
When the cookies have cooled completely, frost each one generously with the peppermint frosting.
After the cookies have been frosted, place them in the refrigerator while you're getting the chocolate ready. Melt the chocolate chips in the microwave for 30 seconds, then stir. Repeat in 10 second intervals, stirring each time to avoid overheating, until you can stir smooth.
Spoon a layer of chocolate over each cookie, spreading it to not quite cover the peppermint frosting. I like to see the edges of white from the top of each cookie.
Immediately sprinkle the remaining peppermint bits on top. Refrigerate until ready to serve or package. Makes approximately 30 cookies, depending on size.