For bones: break pretzel rods into various lengths to make 40 pieces. Microwave ½ cup white chocolate in small microwave-safe bowl on HIGH at 30-second intervals or until melted, stirring each time. Use the melted chocolate to attach 2 mini marshmallows to both ends of each pretzel piece; let dry. Transfer pretzel bones to a wire rack in a rimmed baking pan.

Microwave an additional 2 cups of white chocolate melting wafers in medium microwave-safe bowl on HIGH at 30-second intervals or until melted, stirring each time. Pour melted white chocolate over pretzel bones to coat; let dry.

To assemble: Place 1 cake layer on a cake stand. Spread ½ cup Hy-Vee creamy white frosting on top. Repeat with 2 more cake layers. If necessary, secure layers with cake dowels. Place remaining cake layer on top. Frost top and side of cake with an additional 2 cups of frosting. Press pretzel bones into frosting on cake.