Special equipment: 9-inch diameter stainless steel bowl 7-inch diameter stainless steel bowl 5-inch diameter stainless steel bowl 9-inch cardboard cake round 2 (7-inch) cardboard cake rounds 2 (5-inch) cardboard cake rounds 1 (16-ounce) package ready to use gum paste (available at crafts stores) 1-inch vine leaf shaped gum paste cutter (available at craft stores) 2 (80-ounce) packages ready to use white rolled fondant icing (available at craft stores) Pastry bag or resealable plastic bag Small round pastry tip (#2 or similar)
Preheat the oven to 350 degrees F. Spray each stainless bowl with nonstick cooking spray and coat lightly with flour, tapping out the excess. Put the bowls on 2 sheet trays.
In an extra large bowl add the cake mixes with the butter and combine with a hand mixer. Add the egg whites, 1 at a time, and incorporate. Slowly add buttermilk and mix on medium until well incorporated, about 2 minutes. Fill each stainless bowl 2/3 of the way to the top with the batter. Bake until the tops are golden brown and a toothpick inserted in the center of the cake comes out clean, about 30 to 50 minutes. (Large cake will take closer to 50 minutes, smaller cakes closer to 30 minutes.) Remove the cakes from oven and cool. When cool enough to handle, unmold and cool upside down on a wire rack. You will have 1 (9-inch), 2 (7-inch), and 2 (5-inch) cake domes. Keep any extra batter in refrigerator. Cool down pans in between baking times. If there is still excess batter, bake off cupcakes for shower favors.
For the gum paste leaves, knead and roll out the gum paste to 1/16-inch thickness. Using the leaf cutter, cut vine leaves from gum paste. Using the back end of a butter knife make leaf veins by pressing lightly into the gum paste. Repeat until you have about 80 leaves. Set out on a sheet tray lined with a wrinkled piece of plastic wrap to dry completely. (This step is best done a couple of days ahead of time.) To make loops for around the base of the cake, roll gum paste into a very thin rope. Cut into 3-inch pieces, pinch ends together to form a loop using a dab of water, if necessary, to stick ends together. Dry flat on a sheet tray. (You will need 24 (3-inch) loops for the large cake, 40 (2-inch) loops for medium cakes, and 32 (1-inch) loops for the small cakes.)
Adhere each cake to a corresponding cake board with a dab of icing. Ice each cake in a very thin smooth layer with an offset spatula. Put in refrigerator to set up. Working with 1 cake at a time, put a second slightly thicker layer of icing on cake, being sure to clean the knife frequently to keep the icing smooth. (If icing is too loose try mixing in 1/4 cup confectioners' sugar to stiffen it a bit.) Knead the fondant to soften slightly. Using a flat surface dusted lightly with cornstarch, roll the fondant to a large (1/4-inch thick circle about 18 inches in diameter for the large cake). Lift with backsides of your hands and put over the center of iced dome cake. Using your hands lightly dusted with cornstarch, smooth fondant down and around the sides of the cake. Lift cake up and trim the excess fondant close to the cake board with kitchen shears or a paring knife. Put on a cake pedestal. Repeat until all of the cakes are covered.
To make royal icing for the vines: In a medium bowl beat together the 2 cups confectioners' sugar, the meringue powder and the lemon juice with a hand mixer and slowly add in a little water until smooth. Continue to add water by the teaspoonful with beaters running until the icing will drop from the beaters but hold a line when drawn in with the back of a spoon. Fill a pastry bag fitted with small round tip. Pipe vines for leaves all around the cakes, using long strokes holding tip just off surface of the cake. Adhere dried gum paste leaves in groups along the vines with a small dab of royal icing. Lastly adhere the loops along the base of the cake with a small dab of royal icing as well. Put on the table in descending-size order.