The mysteries of the incredible egg, explained

With certain foods, you have to wonder: Who first gave them a try?

Consider the egg. Broken open, it unexpectedly reveals two different innards, one yellow and globular and the other pale and gelatinous.

Frying an egg may not have taken a great leap of faith. But who figured out how to bake with it? How did people learn that whites whip into peaks and, with sugar, become meringue? Who discerned that protein-rich yolks provide structure as well as flavor in sponge cakes?

Dunno. Yet food historian Harold McGee says that eggs clearly have been used since Roman times. We here in the 21st century are privileged to luxuriate in such past discoveries. But baking with eggs still requires some care and technique. Here are a few questions — and answers! — to help ensure success.

Q: Small, large, jumbo — do egg sizes really make a difference?

A: Somewhat. Although if you're out of large eggs, but have either medium or extra-large eggs in the house, you can substitute either without compromising a recipe.

That's because a large egg weighs about 2 ounces, while a medium egg weighs a quarter of an ounce less and an extra-large egg weighs a quarter of an ounce more, according to U.S. Department of Agriculture guidelines.

When a recipe simply notes "eggs," the assumption is "large." But you can move up or down one size without fear.

One caveat: It's not a big deal to substitute one medium egg for a large one in a recipe, but when you're making an angel food cake that calls for a dozen eggs or if you're tripling a recipe, that slight difference can count up. Consult the American Egg Board's substitution chart at incredibleegg.org.

Q: Why do some recipes specify eggs at room temperature?

A: Ingredients at similar temperatures combine more successfully. If you add cold eggs to a rich batter, that can make the fats harden into small lumps, affecting the texture of the baked product. That's why it's always good to read a recipe through before starting, so you can remove the eggs from the refrigerator a half-hour before beginning. If you forget, the American Egg Board has an easy hack: Simply submerge the eggs in warm — not hot — water for a few minutes.

A room-temperature egg also whips to its greatest volume, especially egg whites. But it's easier to separate egg whites from yolks when eggs still are chilled. So do that first, then let the whites warm up before whipping them; it only takes about 20 minutes, or about the time it takes to prep your pans and other ingredients.

Q: Speaking of separating an egg, what's the best method?

A: Views differ, starting from how to crack an egg. Many home bakers grew up cracking an egg against the rim of a bowl, but you risk a shard of shell falling into your ingredients. Others recommend cracking eggs against the countertop. Do what works best for you.

Here's a tip: If you do need to fish a bit a shell from the whites, use one of the empty shells; it cuts through the whites better than your fingers or a spoon.

But back to separating: You can use an egg separator tool, which is pretty foolproof, but something else to wash (and buy). Or you can carefully shift the egg yolk back and forth between the two shell halves, while letting the white drip into the bowl. The trick here is not to let the yolk get pierced by the shell. Even a bit of yolk in whites will prevent them from beating to their highest volume.

Or you can pour the contents of a broken egg into a slightly cupped palm, letting the white drip through your fingers. If you do this, be sure your hands are spotlessly clean. Any oil from your fingers can also compromise how well the whites whip.

Q: When are pasteurized eggs a good idea?

A: Eggs are quite safe. The Egg Board notes a rate of egg contamination with salmonella bacteria at about one in 20,000 eggs. But if you're making raw or only partly cooked recipes — or serving the very young, the elderly, pregnant women or anyone whose immune system is impaired — pasteurized eggs offer the most food safety. One note: The heating process that pasteurizes eggs may make the whites cloudy and increase the time you need to beat them, up to about four times, to get their top volume.

Q: Some recipes leave me with extra whites or yolks. Can they be frozen for later use?

A: Yes and no. Whites freeze quite well in tightly sealed freezer containers for several months. Thaw overnight in the refrigerator, then bring to room temperature before using.

Yolks are a different matter, tending to become gelatinous when frozen and thawed. The American Egg Board, however, has a novel approach for thrifty bakers: "Carefully place the yolks in a single layer in a saucepan and add enough water to come at least 1 inch above the yolks. Cover and quickly bring just to boiling. Remove the pan from the heat and let the yolks stand, covered, in the hot water about 12 minutes. Remove the yolks with a slotted spoon, drain them well and package them for freezing."

Once thawed, the yolks can be grated for garnishes, used in egg or potato salads, etc.

Q: Is there a difference between brown eggs and white eggs?

A: Nope. Color is linked to the breed of chicken, not the quality of the egg.

Kim Ode, a former Star Tribune reporter, is a freelance writer and baker from Edina. She can be reached at odekim@gmail.com.

Here's a delicious recipe for all seasons. The whites make a pavlova meringue shell and the yolks are used to make a tart lemony curd. One caveat: Meringues are best made on dry days. Humidity may cause them to soften.

Individual Pavlovas With Lemon Curd

Makes 10 to 12.

Note: The recipe is adapted from "BakeWise" by Shirley Corriher. You can make your own superfine sugar by whirring regular sugar in a blender or food processor for 1 to 2 minutes until the sugar feels like fine sand.

• 3/4 c. superfine sugar, divided (see Note)

• 1 c. powdered sugar

• 1 tbsp. flour

• 4 large egg whites, room temperature (save 2 yolks for curd)

• 1 tsp. white wine vinegar

• Lemon Curd (see recipe)

• Fresh seasonal fruit, such as figs

Directions

Preheat oven to 250 degrees. Place rack in middle position. Place a sheet of parchment paper on a baking sheet.

In a small bowl, whisk together 2 tablespoons superfine sugar, the powdered sugar and flour. Set aside.

Using a stand mixer with the whisk attachment, or a hand mixer and large bowl, beat the egg whites and vinegar until foamy, slowly at first, then building up speed until soft peaks form when the beater is lifted. Slowly add the superfine sugar a tablespoon at a time and beat on high until the whites are smooth and shiny and form very stiff peaks.

Sprinkle part of the reserved sugar mixture on top of the meringue and fold in with a few strokes of a large spatula. Continue sprinkling and folding until all of the sugar mixture is folded in.

Pipe or spoon dollops of meringue onto the parchment paper into puffs about 3 inches across, leaving 2 inches between each. Use the back of a spoon to make a slight well in the center of each pavlova.

Place in the oven and immediately reduce heat to 200 degrees. Bake 1 hour and 45 minutes until thoroughly dry. Remove from oven and allow to cool completely. Gently peel meringues off the parchment paper or slide an offset spatula underneath the shells.

Just before serving, fill pavlovas with Lemon Curd and garnish with fresh fruit.

Nutrition information per each of 12 (no added fruit):

Calories230Fat9 gSodium30 mg

Carbohydrates36 gSaturated fat5 gTotal sugars35 g

Protein2 gCholesterol65 mgDietary fiber0 g

Exchanges per serving: 2 ½ carb, 2 fat.

Lemon Curd

Makes 1 1/4 cups.

Note: From Kim Ode.

• 2 egg yolks plus 1 whole egg

• 3/4 c. sugar

• 1/3 c. lemon juice

• 1/2 c. (1 stick) unsalted butter, room temperature, cut in 16 pieces

Directions:

Combine 2 yolks, whole egg, sugar, lemon juice and butter in a medium bowl that will just nestle within a saucepan (you will be making a double boiler).

Pour 1 to 2 inches of water into the saucepan, then place bowl — making sure that its bottom doesn't touch the water — and heat over medium heat, whisking constantly, until the curd thickens. Keep the water at a steady simmer, not boiling. Refrigerate curd until completely cool.