Bake and cool a 2-layer 10 in. round cake. Stack cooled cake layers using buttercream icing or another favorite filling between layers. Place on a foil-wrapped cake circle.
Spatula ice cake smooth with white buttercream icing.
Fill cones with candy-coated chocolates. Tint buttercream icing rose, green, orange, yellow and violet. Pipe tip #9 colored icing "ice cream scoops" over top of cone; smooth with spatula. Sprinkle with jimmies. Insert into cake top; add candles.
Trace scallops onto sides of cake; zigzag tip #2 garland at markings. Attach candy-coated chocolate candies to icing. Attach gum drop top border. Zigzag tip #4 bottom border; attach large spice drops to icing.