Meringue
from Betty Crocker Cookbook, 1950 edition

Interesting historical note: Meringue was originally used to frost cakes. Later it became a popular topping for many pies. Becky L. Diamond's Mrs Goodfellow: The Story of America's First Cooking School [2012] devotes an entire chapter to the evolution of Lemon Meringue pie. The author states "no one knows...exactly how or when [lemon meringue pie] was originally conceived." (p. 158). Mrs. Goodfellow's Cookery as it Should Be (1865) offers three recipes for lemon pudding, some in pastry shells (p. 229, 230 & 243), no lemon pies, and the sole reference to meringue(s) (p. 199) is for small confections, not as topping.

3 egg whites
[pinch of salt]
1/4 tsp. cream of tartar
6 T. sugar
1/2 tsp. vanilla (or other flavoring)

Beat the egg whites and the cream of tartar [with a pinch of salt] until foamy. Beat in the sugar, 1 T. at a time. Continue beating until stiff and glossy. Beat in the vanilla or other flavoring.

For Pies:

Pile the meringue on top of the pie filling, being careful to seal the meringue onto the edge of the crust to prevent shrinking. Also, if the filling is exposed to the oven heat, it may "weep." Swirl or pull up points for a decorative look. Bake at 400° F. until delicately browned; about 8 - 10 minutes. Cool gradually in a slightly warm place, away from drafts. See Lemon Meringue Pie

Note: Too long baking and incomplete blending of sugar causes weeping of the meringue.

Egg White Beating Tips:

There are a few tips to beating air into egg whites and producing a buoyant foam — none of which involve rocket science.

• Don’t let any egg yolk wind up in your bowl. Yolks equal fat, and fat makes it pretty much impossible for the proteins in your egg whites to unravel and start forming bubbles. Fat will coat the proteins, preventing them from becoming friends.
• The bowl and beaters should be absolutely clean. If there is a little oil residue in the bowl or a little hint of yolk in the whites, it will interfere seriously with the formation of air bubbles. Plastic bowls and utensils tend to develop a thin coat of oil over time. Because it’s very hard to thoroughly scrub off that coating, metal, glass, or ceramic bowls are preferred.
• The bowl should also be dry as water will inhibit the formation of the foam.
• Beat the whites at room temperature. The proteins in the whites expand better when warm, so you will get better volume from the eggs. Older eggs also whip more easily because of chemical changes that have taken place as they aged. If you’re making a meringue-based buttercream, room-temperature egg whites are vital. When it comes time to add the soft butter to the meringue, a colder mixture could seize the butter and prevent it from becoming a smooth, cohesive buttercream.
• Adding salt and an acid. You should start with a pinch of salt in the whites, which will help firm up the proteins. About a quarter-way through the beating process, you add an acid to the foam, which stabilizes it and helps keep the bubbles from bursting when you stop beating. Most people use cream of tartar, but one or two drops of lemon juice or vinegar will work as well.
• Add your sugar gradually, not all at once. Adding the sugar slowly will save you a lot of time and potential frustration. If you add the sugar all at once, it will take forever for the whites to whip up, but they do eventually gain volume.
• Use superfine sugar. Superfine sugar will leave you with a smooth, shiny meringue. Regular granulated sugar doesn’t dissolve as well and can leave a rough, bumpy appearance.
• If adding meringue to a pie, make sure to spread the meringue all the way to the crust; otherwise, the meringue might shrink on the filling when you bake it.
• Bake meringues (such as cookies or pavlova) low and slow. Most meringues bake between 200°F and 250°F for about 2 hours. Rather than caramelizing and getting toasty brown like most baked goods, meringues slowly dry out in a low oven without gaining much or any color. They often include a rest in the oven after it’s been turned off to continue slowly baking as the oven cools. This will give you a very dry meringue that’s crisp all the way through. If you prefer a chewier center, test the meringues 20 minutes or so before the end of the baking time. Higher temperatures can cause meringues to crack and brown. A longer bake at a low temperature leaves you with a smooth, shiny, crisp meringue that blissfully melts in your mouth. Note: the peaks of the meringue on Lemon Merinque Pie should brown and is baked at a higher temperature.