If you’ve made vegan buttercream, you have also probably had bad vegan buttercream. Even if you follow the recipe to the letter, things can still go horribly wrong. Part of it is that vegan butter/margarine is less forgiving than regular butter, and part of it is that some vegan frosting recipes are completely dumb. Sorry, not sorry people who write dumb frosting recipes. You know who you are. So here are some tips on frosting, and a tip on frosting tips.
SIFT THE POWDERED SUGAR Powdered sugar, especially organic varieties, tends to have clumps. Sugar absorbs moisture pretty easily, which you have probably witnessed first hand if you have ever had an open bag of it in your kitchen when it’s humid outside. So sift your powdered sugar (cocoa powder, too) to break up any clumps.
SOFT BUTTER MEANS SOFT Let your butter sit out ahead of time until it’s softened. How long depends on the temperature of your kitchen. If you press your finger into the butter, it should make a dent. Do NOT melt your butter. Melted butter does not combine with sugar in quite the same way. If you forget to let it sit out, you can microwave it, but do it in small increments (no more than 5-10 seconds at a time) and check it after every single time.
After 10 seconds in the microwave. 
After 20 seconds (total) in the microwave. Starting to melt, but it will work nicely.
USE THE RIGHT BUTTER I’ve heard people say that vegan butter in tubs does not work, only sticks will do. But if all you can find are tubs , it might seem disappointing. Disheartening even. A baking life doomed to always making frostings that have that gross, greasy, wet snow kind of look to them. But don’t worry, because as with so many things in life, those people are wrong! Vegan butters, whether sticks or tubs, can work as long as you do NOT buy any that are “whipped.” Whipped butter in tubs is designed to spread easier. But since it already has air incorporated into it, it’s going to make things very difficult once you’re trying to cream it with the powdered sugar. So don’t buy the whipped stuff to make frosting and you’ll be okay.
SCRAPE THE BOWL DOWN EARLY AND OFTEN A good rubber spatula or a bowl scraper is your new best friend. Scrape the sides of the bowl down frequently. Things stuck on the side of the bowl or on the beaters don’t often magically get mixed in. They just stay there. So every time after you’ve mixed something in and you see things not getting incorporated, scrape!
START WITH JUST THE BUTTER IN THE BOWL Run the mixer just long enough to get the butter spread out. If you put it and the sugar in to start, you’ll just make a big cloud and get sugar all over.
ADD THE SUGAR AND RUN THE MIXER ON LOW UNTIL THEY START TO COMBINE Most recipes say to cream them at this point. If they combine enough to cream at this point, great. But they probably won’t. Non-dairy butter works like the regular stuff, but there are still some differences, and this is one step where you will usually see that. Let them just come together, and then it’s time to add a little liquid.
ADD YOUR FLAVORING NOW, BUT HOLD OFF ON THE OTHER LIQUIDS Remember back in step 1 when I said sugar absorbs moisture? That’s why frosting recipes usually have a range of whatever other liquid (water, milk, whatever) they call for. You will not know how much it needs until you start to mix it, which means there is a bit of trial and error involved. After I add my extract(s), I let the mixer go on low speed and see how it looks. If it’s still not coming together, I’ll scrape the bowl down with a rubber spatula, turn it back on to low and add half off the liquid the recipe calls for, letting it mix another minute or so. Still too dry and chunky? I’ll add smaller amounts of liquid and repeat this process until it looks like a very thick frosting. Then it’s time to turn things up a bit.
MIX ON HIGH SPEED, BUT NOT TOO HIGH My mixer has speeds labeled 1 through 8. Once my buttercream starts to form, I run it on 4 for about 4-5 minutes. If you mix your buttercream at too high of a speed, you run the risk of incorporating too much air. This becomes a problem pretty quickly when applying the frosting. It looks runny, collapses, and makes things frustrating. So a medium-high speed is the way to go. Patience is a virtue! I just came up with that phrase myself. You can use it though. Once you have the texture and consistency you are looking for, you are ready to decorate.
USE THE RIGHT TOOLS FOR THE JOB Decorating cupcakes? You will need a piping bag or two, a large star shaped tip, and maybe a round one. Decorating a cake? Same as the cupcake tools, but get an offset spatula (a small one works best unless you’re doing a massive cake, then get a bigger spatula). If you want to try more advanced piping, like borders, writing, flowers, whatever, then get the tips for those. But if you go overboard and buy a million tips, you’re probably going to end up with a drawer full of them just collecting dust. I use two bags and three tips for about 90% of the decorating I do. I have some tips that I have never used and almost certainly never will. And yet I can’t bring myself to get rid of them just in case I ever need them for something (spoiler alert: I won’t). So if you’re just getting started with cake decorating, only buy what you need. It’s easier to add to your collection as needed than ever figuring out why you have 10 leaf tips with duplicates of 3 of them.
