Put wax paper on the edges of a large cake platter. Best is a footed platter than you can turn around, Place one wafer on the plate, then spread blackberry preserves on it. Then put another wafer, and spread rose preserves on that, then the third and fourth layer are Nutella. Then put the "cake" in the refrigerator over night so the layers can stabilize, at least 12 hours.. To make the ganache, put the bowl, beater and cream in the freezer for at least 20 minutes or until the cream is so cold it is almost frozen. Put the chocolate in a double boiler and melt over simmer water, stirring frequently. When it is almost all melted, add half of the cream. Put the rest of the cream in a mixer and beat it until you can see patterns, but not until stiff peaks form. Carefully add the melted chocolate, and beat again until stiff peaks form. Take the cake out of the refrigerator, and plop a large amount of the ganache on top, then spread it around and on to the sides. When it is completely frosted, you can put on the decorations. When you are finished decorating, put it in the refrigerator until ready to serve, at least 3 hours. Remove wax paper before serving. It is best to cut this with an electric knife, and tell guests to eat their slice like a sandwich, as a fork does not do well with this cake.