My 12 year old daughter wanted a sleepover cake, but doesn't like fondant and wanted me to use butter cream icing. We made a lemon cake and baked it in a 9x13 pan.
Once cooled, I cut one piece at 5" and the other was left at 8". We filled the portion that was double layered and then did a crumb coat of plain butter cream and placed it in the freezer for about 30 minutes. While the cake was chilling, we mixed butter cream icing in a batch of Carolina Blue and Bright Yellow.
Then, I rolled out some pre-colored fondant and used a pizza cutter to make a 14" strip to act as the blue sheet folded over on the bedspread. I used yellow gel to make dots across and sprinkled the yellow/blue/white candy coatings on top. We then cut out large and small circles in the blue and a pastel green fondant. The small circles were "glued" to the big circles in opposing colors with a drop of water and a Qtip.
Now time to decorate the cake. Be VERY generous with the icing as you will wipe quite a bit off when you smooth it to appear as fondant. Ice the lower, single portion in light blue and take it up on the sides as this is the sheet. Then ice the bedspread portion (we used bright yellow) and make sure to ice all the way to the drop off level so it will hold your pre-made fondant strip. You heap the icing on and then use a flat icing spatula (metal) and as you make a pass across the cake, wipe off the excess icing from the spatula and place it in bowl of water to help smooth the next pass across the cake. This gives butter cream the look of fondant.
We added the fondant strip "sheet fold over" and then got the vanilla wafers and added a dollop of icing on the back to hold them down. We then tinted more butter cream to match the colors of hair of the party girls. I used an icing piping tool to create the hair. You can use a Ziploc bag with icing and squeeze it out if you don't have a tool. The eyes were edible icing gel.
Tips: Water acts as glue for fondant For this Sleepover Cake, use one box of cake mix and 4-5 tubs of butter cream. For Carolina Blue coloring, we used blue food coloring and added a drop of red.