Placing Filling Between Layers
You may want to put two leveled cakes together, joined with your favorite filling.
Fill a decorating bag with medium consistency icing. Use either tip 12 or just a bag with a coupler without adding a tip. If you have multiple layers, start with the bottom layer, leveled side up. Pipe a ring of icing around the entire cake just inside the edge to create a dam or circle of icing. This will prevent any filling from seeping out when the next layer is added. The ring should be about 3/4" high and 1/4" from the outside edge of the cake.
Fill in the dam with your choice of filling. Buttercream, pudding or thick-consistency fruit fillings can be used.
Place the next layer on top, making sure it is level. The weight of the layer will cause the circle of icing to expand just right.
Repeat until all layers, except the top, are assembled. Place the top layer, leveled side down, so the top of the cake is perfectly smooth and level.