If i were to use custard as a filling for my cake, would i have to put a thin layer of buttercream on the cakes to prevent the custard from seeping into the cake?

I have never used b/c before i put any fillings. Never had a problem.hth

It really depends. If your filling is a thick custard and the cake doesn't absorb it, there is no need.

However, this is a classic pastry technique to keep the original consistency of pie crusts, pastries, and cakes. Often, they are brushed with a thin layer of melted apricot jam as a sealant. Of course you could use other flavors or even buttercream.

A great example would be a fresh berry pie with a pre-baked shell. All of those berries and sugar might make the pie shell soggy. But if you seal it first, it is nice and crisp.

I do the same to cakes if I want a macerated berry filling.

You can also brush a thin layer of melted chocolate to waterproof the cake.

Thanks! I appreciate the feedback. I think ill try putting either the melted jam or chocolate since i use ganache to ice the cake.