First time making SMBC and I followed this recipe: https://livforcake.com/swiss-meringue-buttercream-recipe/ 

I started adding the butter and it just kept getting even more runny! I have searched online and the only answer I’ve been able to find is put it in the fridge for a while then rewhisk so I’ve tried doing this and it seemed to work until I mixed it a little and it turned liquidy again! 

How can I save it???

if it is liquid it sounds like your meringue was too hot and melted the butter —

if it looks curdled you should be able to whip it into shape but if it keeps dissolving re-read the first sentence ^^

a hail mary idea — chill it in the fridge for five or six hours until thoroughly cold — beat it again and see if it will hold up for you 

so i’m sorry to say it might not be savable —

by the time I get my hot off the stove meringue beaten I add cold butter and i’m good but i’ve been making it forever — you gotta be sure your meringue doesn’t melt the butter — 

did you maybe use your butter too soft?

also — there is some kind of new member delay on being able to "reply" to posts so please start a new thread to continue any discussion -- at some point all of a sudden you will be enabled to "reply" but not for a while -- maybe like 30 days — I think it might have to do with time and activity levels -- please respond in a new thread if you want/need to —

best to you

I agree with -K8memphis (of course I do, I ain't stupid!) that the meringue was probably too hot.  It should be no more than barely warm to the touch, when you put your hand on the mixer bowl.  The butter should not be straight from the fridge, but it should not be room temp either.  Let it set out 10 or 15 minutes before using.

The first time I made SMBC, I had to beat it for almost an hour because I added the butter at room temp and too quickly, but it did finally come together beautifully.  Since then, I make sure the meringue is no more than just warm and the butter is still firm.

1. Did you whip your meringue to stiff peaks before you started adding the butter? If the meringue was too soft, it won't hold the structure and probably isn't savable.
2. If that's not the problem, how long did you put it back in the fridge for? I'd say 30 minutes and then try to whip it again. If it's still runny, another 30 minutes and whip again. Sometimes you have to whip it for a long time to get it to come together. 
3. Did it look curdled like cottage cheese? Or just soupy like melted ice cream? If it looked curdled, it's actually too cold, not too hot. Scoop about a half to a cup of the curdled mess into a microwaveable bowl. Microwave for about 15 to 20 seconds until it's melted. Pour it back into the mixing bowl with the rest and then whip again. 
4. Is your kitchen really hot? Maybe it's just too warm to keep it from melting all over again when you try to whip it. 

The tutorial is right on target for proper SMBC making, with good photos.

Interestingly, the tutorial that you posted has the answers to all of your questions at the end of the page.  

""""" I find it best to walk away and come back after 5 mins to a (hopefully) perfect SMBC. See Troubleshooting section below if this is not the case.""""""

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