Making a 10” round vanilla cake with chocolate custard fill. Today’s Tuesday, it’s for this Saturday. I normally make my cakes in advance and freeze, but I won’t this time because the custard will make it soggy upon thawing. How many days in advance would you do a custard filled buttercream cake? I work in a grocery store and our cakes with custard fill have a 5-day shelf life with no issue, but doing it at home makes me nervous. Yes, I plan to pipe a buttercream dam first and maybe a very thin layer of buttercream in between layers so custard doesn’t seep in. I’m worried about the sides bulging and sogginess if I do it too early. Thoughts? 

Not sure what recipe you use for custart but what I have used has never soaked into the cake.  I am very skeptal about u sing b'cream under (or even over) custard.  

gotta make sure it doesn't slide if you do the buttercream layers like that -- yes and as lynnie says -- depends on the recipe -- you cooking it or using from a sleeve or instant? so many different ways to go -- sleeve would prolly be fine -- cooked, maybe ok and instant I would do the day before --

best to you