Chocolate Peppermint Sandwich Cookies

Name: Chocolate Peppermint Sandwich Cookies
Ingredients: 2 1/4 cups all-purpose flour; 1 teaspoon baking soda; 1 1/2 teaspoons cornstarch; 1/2 teaspoon salt; 3/4 cup unsalted butter, melted; 3/4 cup loosely packed light brown sugar; 1/2 cup granulated sugar; 1 large egg plus 1 egg yolk, at room temperature; 2 teaspoons pure vanilla extract; 1/2 cup semi-sweet chocolate chips; 1/2 cup festive M&M's; 4 ounces cream cheese, softened; 4 tablespoons butter, at room temperature; 1 cup confectioners sugar; 1/2 cup crushed candy canes