If you’ve ever frosted a cake, you may have encountered one of the most common problems with homemade cakes; that is frosting full of cake crumbs. There is an easy way around it, and that’s to do what’s called a crumb coat.
Once the cake has been assembled (sliced and filled if necessary), take a small amount of your frosting and spread a thin layer all over the cake making sure that no cake is left exposed. Chill this until it’s all set up, and then do your final layer.
As long as you don’t scrape any of the crumb coat into your top coat, all the crumbs will stay there and not be seen.