HI Karen!
When you use custard fillings you want to pipe a buttercream border (barrier) around the perimeter of the cake and then fill the center with the custard. (makes sure you don’t fill it above the piped border, otherwise this will cause your cake to shift on you) Then once your cake is filled, just ice the cake as normal. Yes, you want to put this cake in the fridge because it has eggs and cream in the custard.
Danielle - Sugar's Silk™
