Dissolve gelatin in cold water and the bowl over boiling water to melt on steam. Stir the gelatin in between and take out the bowl from boiling water pan until all the gelatin melts completely.
Make small holes in the marble cake at equal distances using skewer.
Pour the melt gelatin over the cake and refrigerate for 2-3 hrs until gelatin sets completely.
Meanwhile prepare frosting for the cake, cream butter and sugar until become fluffy.
Add cocoa, milk and vanilla and mix well.
Cover the cake with the prepared chocolate frosting and decorate with candy pumpkins.