I once did a communications workshop where the instructor told us that the worst way to begin a speech or address was to say how boring it was going to be because the audience will automatically tune out. So I'm putting that story out there but saying no more...
Swiss Meringue Buttercream Icing (from now on SMB because I'm a lazy so-and-so) is the rolls royce of frosting. Light and fluffy, its like eating a buttercream so smooth it feels like whipped cream. But before you start furiously separating eggs I would advise caution. My frosting ended up a curdled scrambled egg like mess and only for this website I would have had to chuck it in the bin. Luckily the advice in this (invaluable) blog post (SMB HELP!) actually works and got my frosting back on track, silky and delicious.
Here are a few things I learned
A. Be prepared, cube your butter, have everything at room temperature, have ingredients weighed and food processor/beater organised.
B. Pop it in the fridge if you feel that it is too light/soft. If after 30 minutes its still too soft beat again.
C. Make sure there are no little lumps of butter in your icing.
D. Use a sugar thermometer.
E. Watch this video- she simplifies it a lot but at least you can see the textures and get a rough idea of what you're looking for. Dyann Bakes SMB
From 'How to Eat a Cupacke'
170g caster sugar
3 egg whites
1/8 tsp salt
170g unsalted butter
1. Place the salt, sugar and egg white in a heatproof glass bowl over a pan of simmering water. This is called a bain marie. The bowl should not touch the bottom of the pan so you might need to fiddle around with your collection of bowls and pans to get a bowl that sits in about half way but doesn't touch the bottom.
2. Beat constantly until the thermometer reads 140-160oF (different sources say different temperatures, I presume within the range is fine). Now you have pasteurised your egg whites so they are safe to eat.
3. Take off the heat and beat with the whisk attachment of your food processor until the bowl is cold and the egg whites are thick and shiny. This will probably take about 6-7 minutes.
4. With the paddle attachment of your food processor (as per Dyann bakes) add the butter cube by cube beating well after each addition. Increase speed and beat for 4-5 minutes until the icing is thick enough to hold shape on the top of the cupcake. If you think it is too light stick the bowl into the fridge for 30 minutes. If your icing has gone curdled/separated follow the tip in the blog above and heat 1/4 of the mixture in the microwave for 10 seconds, then add back into your icing and beat thoroughly.
5. Fold in any flavours or colours (although I wouldn't advise using liquid-y colours as they could mess up the consistency, use gel colours preferably).