Heat oven to 375°F. Line 2 cookie sheets with either parchment paper or silicone baking mats. Set aside.
In a large bowl, mix cookie mix, softened butter, water, and egg with a spoon until soft dough forms.
Drop dough by rounded teaspoonfuls 2 inches apart onto ungreased cookie sheet. Bake for 6 to 8 minutes or until edges are set. Press 1 peppermint pattie on each cookie; cool for 2 minutes on a cookie sheet. Remove cookies to cooling rack. Cool completely, at least 1 hour.
In a medium microwavable bowl, microwave chocolate chips and whipping cream uncovered on High for 1 minute; stir. Microwave in 10- to 15-second intervals, stirring after each, until mixture is smooth. Spoon a generous teaspoonful on top of each peppermint pattie on the cookie; spread to cover the candy. Sprinkle with candy sprinkles.
Refrigerate cookies until set, about 15 minutes. Store covered in an airtight container at room temperature with waxed paper between layers.