In a large mixing bowl, beat 14 tablespoons butter and 4 tablespoons cream cheese until creamy and smooth. Add ½ cup powdered sugar and peppermint extract and beat until fluffy.
In a small mixing bowl, mix together flour,  cornstarch, and salt. Add dry ingredients to wet ingredients and blend until incorporated. Cover and chill for 1 hour.
Preheat oven to 350 degrees F.
Scoop dough with cookie scoop into 1-inch balls. Roll and place on baking sheet. Use the bottom of a cup to flatten cookies, and bake for 10 - 12 minutes or lightly browned on edges.
Make frosting by mixing butter, powdered sugar, milk, vanilla extract, and food coloring with a hand mixer in a medium bowl. Add more milk until it’s the desired consistency.
Frost cookies and sprinkle with crushed peppermint pieces. Let set up before packaging or storing.