Preheat oven to 375 degrees F.
In a large bowl, cream together butter, shortening, and sugar until fluffy.
Add eggs, one at a time, mixing after each.
Mix in the vanilla.
Measure out the flour, salt, and baking soda & sift.
Add into the sugar/egg mixture.
Combine but don’t over mix.
Spread and press dough onto a sheet pan (18"x13"x1") lined with parchment.
Bake for 20-22 minutes, or until golden brown; let cool completely.
Spread frosting in an even layer on cooled cookie bars and top with crushed peppermint candy.
In the bowl of a stand mixer fitted with the paddle attachment or a large mixing bowl with a handheld electric mixer, beat the butter on medium-high speed until creamy and pale in color, about 5 minutes.
Add half the powdered sugar & beat on low speed just until the sugar has fully moistened, then turn the speed up to medium-high and beat until well incorporated, about 3-5 minutes.
Add the remaining powdered sugar and beat on low speed just until the sugar has fully moistened, then turn the speed up to medium-high and beat until well incorporated, about 3-5 minutes.
Add the peppermint oil, salt & pink food coloring.
Turn the mixer on low speed and slowly add 3 tablespoons of the heavy cream.
Turn the mixer up to medium-high and beat until the cream is well incorporated, about 3-5 minutes. (After 2 minutes stop and scrape down the sides and bottom of the bowl then continue mixing.)
Check the consistency of the frosting and add more cream, 1/2 tablespoon at a time, if needed.
The frosting should be soft and spreadable but not so loose that it doesn't hold its shape.