Greggy’S Very Vanilla Swiss Buttercream - cooking recipe

Ingredients

8 ounces by liquid measure egg whites (I recommend using real eggs, avoid carton egg whites, About 4-5 large eggs)
2 cups sugar (granulated, avoid powdered sugar)
1/2 teaspoon cream of tartar
3 cups unsalted butter (room temperature and yes, unsalted makes a difference)
1 pinch salt
4 teaspoons pure vanilla extract (it will be on the ivory-side if you use regular Vanilla. You can use clear vanilla if you'd like for)
2 teaspoons vanilla bean paste (extract mixed with vanilla bean specks, or vanilla bean extract)

Preparation

Place sterilized stand-up mixing bowl (just make sure it's super clean and dry) with whites on top of a sauce pan with water, barely simmering (a.ka. double boiler).
Heat to 160 F, constantly stirring. Be sure to watch it and keep stirring or else it'll turn into an omelette.
Add Cream of Tartar and whip in stand mixer until cool. Place in refrigerator or freezer if necessary, after reaching a medium peak. You can also place the cooked egg whites on an ice bath ahead of time and place it in the refrigerator, then whip it up.Place back on whip and gradually add butter, one stick at a time. Make sure the meringue is cold prior to adding it to the mixture or else it will be a soupy mess. The mixture should separate at first (don't be alarmed and freak out). Be patient and keep mixing; it'll come back together. Mix until smooth and well incorporated.
No Cook Variation:
You could beat powdered egg whites (the kind where you just add water and whip), then proceed with the recipe (without Cream of Tartar).