World's Best Swiss Buttercream Recipe

Swiss Style Meringue Buttercream
recipe from www.woodlandbakeryblog.com

This Recipe Can Be Stored for 4 days room temperature, 2 weeks refrigerator, 2 months freezer
Yield: 6 Cups: Enough to ice 30 Cupcakes, or Fill and Ice 1- 8" Cake

Ingredients

Fresh Large Egg Whites 180g (6 Large)
Granulated Sugar 300g (1 + ½ cups)
Confectioners Sugar 240g (2cups)
Solid Vegetable Shortening 170g (3/4 cup) **See Note Below
Unsalted Butter 454g (2 cups)
Vanilla Extract Or Vanilla Paste 1 Tablespoon

Instructions
Over a double boiler, in a large metal bowl whisk together the granulated sugar and the egg whites stirring constantly until the mixture reaches approximately 115 degrees F and the sugar grains have dissolved and are not longer gritty to the touch.
Pour this mixture into the metal bowl of your Kitchen Aid Mixer with the WHISK attachment and whip on high speed until it is thick, glossy and white in color. The peaks should be as firm as firm can be.
In the meantime you can sift your confectioners sugar, and once you have achieved STIFF peaks meringue, add the confectioners sugar all at once with the mixer on very low speed to avoid having a snow shower of sugar all over your kitchen!
Once all of the sugar has been incorporated you can turn the mixer speed to med-high until it is all nicely mixed in.
Be sure your butter and shortening are at room temperature and they are the same consistency. Add it in about 2-3 additions, but FAST Additions.
Switch to the paddle attachment and continue mixing on low to medium speed until smooth

Notes
This Recipe Can Be Stored for 4 days room temperature, 2 weeks refrigerator, 2 months freezer