italian buttercream - Page 2

Buy a nice shiny KA mixer. Now you are hands free to stream the molten sugar and drop the chunks of butter. If you get the scrambled egg problem corrected and the BC seems to break anyway (curdled looking) keep dropping in the butter. When everything is in, place your bowl of curdled BC in fridge and leave it alone until cold. Then put back on your machine and beat the crap out of it. It will come together.

Another thing to consider when you have been making Italian BC for years and it suddenly wont work is the actual butter itself.  The only batches of soupy frosting I have made were using cheap butter. 

With the benefit of experience and an open mind I can say that a deft hand at pouring the syrup will eliminate most, if not all of the clumping problems.  In addition, a higher sugar syrup temperature should not adversely affect your final product, not even really cook it that much more.  You already beat your egg whites to a nearly stiff peak when you add the sugar so it's just a huge collection of air bubbles, heat simply doesn't travel well through this network.  A few degrees above shouldn't cause problems.  Actually, Herve This postulated about making Italian meringues with a higher sugar temperature, so the possibility is there.

Italian buttercream ? Never heard about it here!.

Actually this is a shortcut term to refer to buttercream based on meringue italienne - I don't know how common that is here in italy, but in other languages they often use terms for a specific meaning - florentine means with spinach - whether or not the actual dish is typical of florence. 
Meringue italienne is "italian meringue" which is eggwhites that are beaten and a hot sugar syrup is beaten into them which stabilizes them and cooks them at the same time.  Then butter is beaten into it when it's cool.  The meringue (minus the butter) also makes the absolutely best ice cream - mix it with whipped cream and freeze, and you have an ice cream without any crystals, without an ice cream machine - and if you add melted chocolate to the meringue and beat it all till cooled and then add whipped cream to that, you have the absolutely best chocolate ice cream (for my taste anyway). 

While I agree with some of the method suggestions you have been given, the major flaw I see is that your egg white, sugar, butter ratio is off. Classical Italian Buttercream is a 1:2:3 ratio. Your listed ratio is a 1:2:2. You are short on butter, 1/2# short for the recipe you listed.

 

This style of frosting is an emulsion; 1/2 formula, 1/2 recipe; there is lots of science going on here!

 

Other things to consider:

 

Temp, temp, temp.  @ 230, start whipping, @ 240, start pouring; no more, no less.  Thin, steady stream- aim for the space between where the whip spins and the side of the bowl.

 

Make sure you don't go past soft peaks with your whites. 

 

Cream your butter, vanilla and lemon first. A light and fluffy butter mix combines into the meringue easier than chunks. Add it a spatula full at a time to help the emulsion process, starting with a small scoop and getting gradually larger with each addition. Allow each addition fully incorporate before the next addition. Just like making hollandaise or mayonnaise, you don’t just throw in your oil all at once.

 

Get all of your ingredients to room temp before beginning. Egg whites whip better at room temp and they will be less likely to cool off your syrup as some have suggested.

 

"Whip it good!"- let the meringue cool after the syrup is in...it can be just slightly warm to the touch, but give it due time in the mixer, mixing on high until it is cool. Usually no less than 15 minutes, but up to 1/2 hour. A trick- every 5 minutes or so, slowly lower the bowl while mixing to break up the top layer. The top layer acts like a layer of insulation and holds the heat in; you might even see some steam escape the first time you do this. But be careful, I don't think OSHA would recommend this process

 

Good luck!