On my way into work today with yet another layer cake (about which more to come later), it occurred to me that the entire time I was growing up, my mother baked cakes but never once made a buttercream frosting. By “buttercream” I mean a proper buttercream — made by beating butter into a meringue — not the sweetened grease that too often goes by the name of “American” or “easy” “buttercream”. The frosting I remember from my childhood definitely falls into that second category: nothing more than Crisco whipped with a pound of confectioner’s sugar, a few tablespoons of milk or other water-type liquid added to adjust the consistency. No wonder my mother was (and is to this day) disgusted by frosting, when that was what she was used to! That is essentially the same substance as the filling used in Oreos (and of course back in the days before Crisco, people would have used lard, just like in Oreos). Proper buttercream is much nicer, despite having even more fat than the imitation stuff. On today’s cake (yesterday’s by the time you read this), I received comments like:

That lemon frosting is addictively delicious and the texture is just wonderful. … I was so overwhelmed by the frosting that I only remember the cake as a pleasant vehicle.

It’s a bit of a pain to make, since it requires a stand mixer, a hot sugar syrup, and a bunch of egg whites. Unless you’re making something like a custard that leaves a lot of leftover egg whites, you’ll probably find that using packaged pasteurized egg whites (sold in one-pound cartons in the refrigerated case at your local supermarket) is much easier and cheaper than separating fresh eggs and finding something to do with the yolks (which, unlike the whites, don’t freeze well). According to my officemate Linda, what I’m describing is technically “Italian meringue” buttercream; there are also French and Swiss varieties, which differ in preparation somewhat. Some buttercreams are also flavored and enriched further by mixing in pastry cream, lemon curd, melted chocolate, caramel sauce, or whipped cream, depending on the application, but I’m concentrating here on just the standard white stuff.

The procedure is simple: make a syrup from granulated sugar, corn syrup (or some other syrup that’s high in simple sugars like glucose and fructose), and water; cook it to 240°F (115°C) — although Linda says her recipe specifies 248°F (120°C). Some flavoring ingredients — like coffee or lemon juice — can be added to the syrup, but most flavorings are added at the very end of the process. While the syrup is cooking, whip egg whites with salt and cream of tartar to soft peaks. Once the syrup has come to temperature, gradually add it to the whipped egg whites to form a sweet meringue — some recipes, like the King Arthur Flour recipe I used this weekend, say to stop the mixer briefly and add the syrup by fourths, but other recipes say to leave it running and carefully drizzle in the syrup. (Since the syrup is both very hot and very sticky, it is important either way to make sure it does not get flung or splashed out of the mixing bowl and onto the cook or innocent bystanders!)

At this point, the meringue must be whipped continuously while it cools down to room temperature; this may take anywhere from 15 to 20 minutes. (For those worried about food safety, the hot syrup should sufficiently cook the egg whites, but if unsure, you can do like I did and use pasteurized egg whites. Be aware that these do not whip up as light and fluffy as fresh egg whites.) Once the meringue is down to room temperature, room-temperature butter and/or vegetable shortening (according to your preference and dietary requirements) is whipped in, a tablespoon or so at a time, and then flavorings and colors can be added. The total preparation time is a bit over half an hour, and the resulting fluffy white buttercream frosting keeps at room temperature for several hours, tightly wrapped in the refrigerator for several days, or in an airtight container in the freezer practically forever.

The King Arthur recipe that I used most recently gives these proportions:

I actually used a slight modification of this, since I was making a lemon-flavored buttercream. When I did Daffodil Cake back in June, it used the same buttercream straight, without additional flavors or colors, and you can see some more photos of the process in that post.

Nutrition

I wanted to compare the nutrition of a proper buttercream to the sweetened-grease method, and conveniently King Arthur provides a recipe for the latter (which, to their credit, they call “Fluffy White Frosting” without mentioning the “b” word) with just about the same yield. (They are intended to be substitutable, and in fact this weekend’s recipe calls out lemon-flavored variants of both.) Both recipes make sufficient frosting for one two– or three-layer cake (nine or eight inches in diameter, respectively). This presentation assumes you cut the cake into 16 uniform slices. As you can see, the top-line calorie numbers are nearly identical; where they differ is in how you get there — the proper buttercream uses fat and protein, whereas the Fluffy White Frosting has less fat, no protein at all, and a lot more sugar — some people find it intolerably sweet, in fact.