1. Slice rounded top off each cake layer with a serrated knife so the top of each layer is flat. Cut each cake layer in half horizontally. Lift the top half off, using a broad spatula or the bottom of a tart pan, and place it on wax paper.

2. Cover 3 cardboard cake rounds (6, 10, and 14 inches in diameter) with aluminum foil. Center the 6-inch round on the 10-inch round, and poke a hole through both, using the tip of a knife or an ice pick. Stick a 1/4-inch wooden dowel through both rounds to widen holes.

3. Spread a small amount of frosting in the center of the 14-inch cardboard round, and place 1 (14-inch) cake layer on top. Spread about 1 1/3 cups Apricot Mousse Filling over surface of cake layer, spreading to within 1/2 inch of edge. Top with another 14-inch cake layer. Repeat the procedure with filling and remaining 14-inch layers, ending with cake.

4. Center the 10-inch cardboard round on top of the 14-inch tier. Using the tip of a sharp knife, trace around edge of round; remove round. Cut 6 plastic straws equal to the height of the tier.

Insert straws inside the perimeter of marked circle, spacing straws evenly to support the weight of the other tiers. Spread about 1 1/2 cups Buttercream Frosting around sides of tier and about 1 1/3 cups frosting over the top. (This small amount of frosting is just enough to coat the surface of the cake, sealing in the crumbs so that the second coat of frosting spreads on smoothly.) Place the tier in the refrigerator until it?s time to assemble the entire cake.

5. Assemble the 10-inch tier following the procedures used for the 14-inch tier, using a scant 1 cup filling between each of the layers, 1 1/3 cups frosting on the sides of the tier, and a scant 1 cup frosting over the top. Place tier in the refrigerator.

6. To assemble the (6-inch) tier, spread 1/3 cup filling over surface of 1 cake layer, and top with remaining layer. Spread about 3/4 cup frosting on sides of tier and 1/3 cup frosting over the top. Place tier in the refrigerator.