I made this very simple 'meringue' butter cream. 40 grams of egg white, mixed with 80 grams of icing sugar over an heated bowl until the nice peaks are there, like you want with meringue. Add a little bit of salt and then mix 120 grams of butter in. I used a bit of vanilla extract and icing coloring.
It all went fine and I had the consistency I wanted and could work with it very well. However I decided to do most of the cupcakes the next day. I left the buttercream in the piping bag in the refrigerator overnight. When i wanted to use it the next day it was 'runny' when it was back at room temperature. It was turned in almost some kind of thick liquid. Mixing it again did not help. I red that storing in the refrigerator should not be a problem, however this was for 'normal' butter cream.
Where did it go wrong, and how can I prevent this next time? Did I store it wrong? Or is the consistency wrong? Or should I handle this 'meringue butter cream' different from normal butter cream?
Thanks in advanced!