I have made SMBC plenty of times. I have a friend who wants a peanut butter flavored SMBC. I normally make peanut butter BC more American style with powdered sugar. My friend prefers SMBC. The cake will be covered with fondant. My fear is that that the amount of peanut butter will make it too soft and it will not hold up. Anyone with experience with PB SMBC under fondant?

I simply add peanut butter to my smbc.  I start with a big spoonful and go from there adding more if needed until I get the taste I want.  

I have covered peanut butter smbc cakes with fondant on several occasions and have never had any issues.  If the peanut butter was liquid-y like an all natural peanut butter, that may be a different story, idk.  But, regular pb is just fine.

Hope that helps ya :)

Very helpful Jinkie. Not using natural just the good old non-organic, mass processed stuff in the jar with the red lid :)

I don't have any advice on this, but I am suddenly craving peanut butter SMB......

You can add anything to smbc. Even fruit puree or liquor. 

I make peanut butter SMBC all the time and is awesome and not extremely soft at all. I've always used the creamy not crunchy PB--- With my kitchen aid I just mix a few tbsps. of PB with some already made SMBC. When it looks mixed I keep adding both until I like it and that's it!! --

Side note**

I saw this some time ago here in Cake Central.--White-cake cupcakes, filled them with strawberry jelly, topped them with a swirl of PB-SMBC and call them 'peanut butter and jelly' cupcakes***

I made them and my kids fell in l.o.v.e. and now I have a reputation of the best baker in the family  lol :D :D :D  

I made peanut butter SMBC just a few weeks ago for my mums birthday cake. I just added smooth peanut butter to taste and it was so yummy.

I combined it with Banana cake and ganache (a mix of milk and dark) for a 'snickers' effect. 

I had no issues whatsoever with the icing being unstable.

brown sugar smbc with peanut butter - over the top!

I actually forgot to say that I made my Peanut Butter SMBC with brown sugar - oops. It is really really good made that way.

How do you make SMBC with brown sugar?? do you just replace the white sugar for brown sugar??

Does anyone know if there's a way to make pb SMBC with flavoring that is not allergenic?

Yep Rosie, that is the way that I do it, I just swap brown sugar for the caster sugar in a cup to cup ratio though and not a weight ratio as brown sugar weighs differently to caster sugar.

Ahhh, thank you bubs1stbirthday!!! ---I'm sure it was awesome with peanut butter. Gotto try that asap!!! :)