How to Make It
Preheat oven to 350°F. Arrange ice cream cones, flat-bottomed sides down, in a 13- x 9-inch baking pan. Prepare cake batter according to package directions. Pour batter evenly into ice cream cones (about 3 scant tablespoons per cone).
Bake in preheated oven until a wooden pick inserted in centers of cakes comes out clean, 28 to 30 minutes. Let cakes cool completely in baking pan, about 25 minutes.
Beat cream cheese and butter in a large bowl with an electric mixer fitted with a paddle attachment on high speed until creamy, about 1 minute. With mixer running on low speed, gradually add powdered sugar, cocoa, and vanilla, beating until just combined, about 1 minute. Increase speed to medium-high; beat until fluffy, about 3 minutes. Transfer frosting to a ziplock plastic bag fitted with a large star piping tip. Pipe frosting onto tops of cooled cupcakes. Garnish with sprinkles.