Preheat oven to 350ºF. Butter and line three 8-inch round baking pans with parchment paper. Butter parchment.

In a large mixing bowl, combine the sugar, flour, cocoa, baking soda, baking powder, whisking until thoroughly combined. Add eggs, buttermilk, wine, oil, and vanilla and beat with an electric mixer on medium speed until all dry ingredients are incorporated. Divide evenly among prepared pans.

Bake for 30 to 35 minutes or until a toothpick inserted in the center comes out clean. Remove from oven and place on a wire rack until cool enough to handle. Run a small knife around the edges of each pan, then gently invert onto wire racks. Cakes should come out cleanly. Allow to cool completely. At this point, the cakes can be frozen until ready to use, up to 1 month. Simply wrap each layer individually in a double layer of plastic wrap and then store inside a large zip top bag. Squeeze out any air to guard against freezer burn.

To prepare frosting, in the bowl of a stand mixer fitted with the paddle attachment, beat butter on medium speed until very pale and creamy, about 8 minutes. Add powdered sugar, a little at a time, mixing well after each addition. Add cream and vanilla extract and beat until light and fluffy, about 6 minutes more. Add more cream or powdered sugar as needed for desired consistency.

To assemble, level each cake layer by cutting of the domed top with a long serrated knife. Place one layer, flat side down, on a cake stand or serving platter. Spread half of the blackberry preserves evenly on top, followed by approximately 1/2 cup of buttercream. Position second layer on top and press to adhere. Repeat with remaining preserves, another 1/2 cup of buttercream, and final cake layer, flat side up.

Cover the entire cake with a thin layer of buttercream. This "crumb coat" will make frosting the cake easier. Refrigerate for about 15 minutes to allow this crumb coat to set. Remove cake from refrigerator and frost with remaining buttercream. Return cake to the refrigerator for at least 30 minutes.

Meanwhile, to prepare the glaze, place chopped chocolate and heavy cream in a double boiler or a heat-proof bowl set over a pot of simmering water. Stir until melted and smooth. Remove from heat and whisk in powdered sugar, stirring until smooth. Add water 1 tablespoon at a time, whisking well after each addition, until the chocolate is of a good pouring consistency. Let cool 10 to 15 minutes or until lukewarm.

Pour glaze slowly on top of chilled cake, spreading to edges with an offset spatula, allowing the chocolate to drip over the edges. Continue pouring until desired drizzle effect is achieved (you may not use the entire amount). Chill until set. From http://www.loveandoliveoil.com