Watch video above to see it made!

1. Meringue is very finicky and does not fluff up well with any oil/grease residue. Make sure you use squeaky clean bowls, beaters, and that no egg yolk is left in your egg whites.
2. Combine sweetener and egg whites together in a heat-safe bowl (or stand mixing bowl) and place over a pot of boiling water (Also known as a double boiler. Be sure water does not touch the bowl.)
3. Heat mixture for 4-5 minutes, or until a thermometer reads between 150-160F, stirring often. (If your mixture is really lumpy for any reason, you can strain it before beating.)
4. If you have a stand mixer, use whisk attachment and begin beating the egg mixture on high speed until it is thoroughly cooled, fluffy, and holds its shape well (beaten to stiff peaks; can take between 8-15 minutes).
5. Switch to the paddle attachment (if using a stand mixer) and begin adding butter little by little. Mixture may become curdled, but will come together after you beating for several minutes. Turn the mixer to high and beat for several minutes to incorporate lots of air and make the buttercream fluffy. Read the tips in the post above for troubleshooting tips if your buttercream isn’t coming together.
6. When it’s nice and fluffy, mix in vanilla.
7. Because this buttercream has liquid sweetener, I find it can make the mixture heavy and sometimes adding a bit of cornstarch or arrowroot powder helps it to fluff up, especially on warm & humid days. This is optional and may not be necessary if your buttercream is fluffing up fine.
8. Use right away or store in an airtight container in the fridge if making in advance. Beat for a few minutes before using to fluff it back up. Makes about 4 cups.