My favourite, Swiss meringue, is made by heating egg whites and sugar over a bain-marie to a temperature of 160°F and then whipping the mixture using a stand mixer for about 5 to 10 minutes until the whisk holds a bec d'oiseau (bird's beak) when lifted. This indicates that the proper stiffness has been reached:
Swiss meringue is stable because the eggs are partly cooked which holds the albumin amino acids in their unfolded state. Unlike French meringue, which is the simple beating of sugar and whites together, the Swiss foam structure is more stable and not prone to weeping. Weeping occurs when the amino acids refold thereby releasing water that was previously orderly arranged around the unfolded amino acids. This is a handy tip for making toppings: switch to Swiss and that meringue pie will not seep water.
Also, Swiss is less fussy than Italian meringue, which is made by adding hot, boiled sugar syrup to beaten whites. There is something contrived, in my opinion, when something as simple as meringue begins to demand a candy thermometer, impeccable coincident timing (you will need to have soft-stiff beaten whites by the time the sugar syrup reaches 240°F) and a level of dexterity to safely pour the syrup in a thin but steady stream into the whipping stand mixer. For all this effort, it is still debatable whether the whites reach the required pasteurization temperature of 160°F because much of the heat of the syrup is lost to the bowl.
All three meringues can be piped into different shapes, such as mushrooms for bûches de Noël as shown in the preceding photo. The type of meringue to use is not so much an issue for baked-through confections - French will suffice though Italian and Swiss are more pliant.
I first discovered Swiss meringue when I made Martha's birthday cake for Patrick. It piped very easily and looked spectacular after being torched. Recently, I used this frosting for our anniversary cake but this time eschewing the use of a pastry bag. I merely swirled the airy mass around the sides then up top, then torched the circular ridges left by my spatula.
Probably the best application is Swiss meringue buttercream (SMBC). Easy, endlessly adaptable, and decidedly grown-up (yet good with kids), SMBC is my favourite icing. It is also rich and decadent so only a small amount is needed when frosting, otherwise the cake may become too cloying.
Many are put-off by the curdling that occurs at some point when butter is mixed into the meringue. As I have written in a couple posts, this is not fatal. More whipping at a higher speed for perhaps another three minutes (maybe longer or shorter) will consistently bring the mixture to a silky smooth consistency. Please refer to the discussion mid-way through this post and the video towards the end of this entry.
SMBC can be frozen for a couple months. I make sure it reaches room temperature before I whipping it smooth or pulsing it through a food processor so that it does not become grainy (this situation would be a mistake, and one that may be difficult to remedy). The latter method produces a buttercream the consistency of mayonnaise. My left-over chocolate SMBC from December was processed this way and used on a small cake which I then complemented with a handful of raspberries. This is shown on the photo below. Also shown is SMBC flavoured with mango purée, which results in a textured frosting that is ideal for a homey approach to cake decorating. Click over the photo to enlarge.
Oil and fats are the enemies of meringue. The slightest bit anywhere (bowl, beaters, hands) will mean that the meringue will not form. There is fat in yolks, so there must not be a trace of it. Once, I couldn't figure out why my meringues would not form - it turns out that my silicone whisk was to blame. Silicone and plastic utensils can have oil residues on them that are hard to wash off.
To make Swiss meringue, combine 1 cup of granulated sugar and 4 egg whites in a scrupulously cleaned bowl of a Kitchen Aid mixer. Whisk continuously over a bain-marie for 3½ to 5 minutes - until an instant read thermometer registers 160°F. Transfer the bowl immediately to the stand mixer and whip at high for 5 to 10 minutes until a bec d'oiseau can be formed when the whisk is lifted.
If pasteurized liquid egg whites are used, you will only need to whisk over the bain-marie until the mixture is hot to touch and the sugar has completely dissolved.
For the longest time, I couldn't get my meringues to dry completely. It turns out that a generous dusting of confectioner's sugar before the meringues go in the oven helps a lot.
On the history of meringues, European cooks in medieval times created egg white foams by beating it with a stick, however it wasn't until the 1600s that the first documented confections of egg whites with sugar was published (D. Muster). Then in 1720, the Swiss pastry cook Gasparini "invented" meringues as we know it (P. Montagné, Larousse Gastronomique, 1988). Another couple centuries later, came the most famous incarnation of meringues - the pavlova.