I have been using the same buttercream recipe for so long now. I go to make it today because I have a wedding cake due tomorrow and it almost turned into a jello-y custard!!

I dont have my stand mixer anymore so I am mixing it with a hand mixer. Could this be why?

I am in panic mode because I don't have much time at all to get this cake done!!

Can you recheck your recipe and measurements? Maybe used cups instead of pounds for your powdered sugar? Try adding more powdered sugar to see if that will stiffen it up? Is the heat different? I wouldn't think just the change it mixer unless it has something to do with the sugar. All I can think of at the moment, sorry. Good luck with it.

Hi selfconclusion12, I know this message is a little late for the cake you're working on. However, I was going to suggest that it might be the heat. If it's been warm and if you don't have air conditioning on yet, it could be a reason why your buttercream wasn't coming together. (Had that happen to me once a couple years ago.) ... Just an idea for future cakes.

If you are using shortening in your buttercream, it might be that the shortening is now trans-fat free. That makes a big difference in the consistency of icing.

Ah, yes. I'd vote for trans fat free shortening. It is the devil.