Basic, Swiss buttercream—fast and simpler. It's from my daughter, Andrea. However, the one on the right is the one I use more often. It's a half recipe, just the right amount for a store-bought cake mix even when done in three cake pans (instead of the usual 2).
1. Heat over bain-marie until 85° Celsius (185° Fahrenheit). I find this too hot and it leads to cooking the egg whites. Instead, I stop anywhere over 140° Fahrenheit.
2. Whip until room temperature. I rub the sides of my KitchenAid® bowl with handfuls of ice cubes or plunge the bowl (carefully) into a sink with enough cold water to go up the side (or I do a little of both).
3. While still whipping, slowly add the butter until smooth. I like my butter colder to compensate for the heated egg white, but also because I often make chocolate buttercream. If too cold, the buttercream will be grainy. No matter, just beat longer or let it warm up a bit and beat again. Buttercream can be very forgiving.
4. Add vanilla to taste; can add slightly melted chocolate. (I melt mine in a bain marie, then set it aside to cool while I'm making the rest of this recipe.) I compensate for the temperature of the chocolate by leaving some of the butter at refrigerator temperature, but this sometimes makes me beat the frosting longer as lumps of butter persist.
Store in refrigerator tight against the depredations of oxygen. It will last even longer in freezer, up to a couple of months.
This complicates the recipe. If you put the cream cheese in with the butter, you'll surely get a grainy mess. The secret is to incorporate cream cheese after the buttercream is made and only once the cream cheese has sat on the counter (outside the refrigerator) until it reaches the same temperature as the buttercream.
My daugher recommends: