Updated January 2012.
The items in The Perfect Pantry fall into three categories.
Use it once a day (onions, mustard, spices),
Use it less often, but in many ways (pasta, chili paste, rice).
Use it only one way, but for that one way, nothing else will do.
Meringue powder is one of those one-time, one-way items.
Once a year, when I'm organizing Drop In & Decorate Cookies for Donation events, I stock up on dozens of ounces of meringue powder, which is nothing more than dried egg white mixed with sugar, cornstarch and arabic gums to stabilize and bind it. When mixed with water and confectioners sugar, meringue powder has the same consistency as beaten egg whites, but magically it morphs into royal icing. And when royal icing is colored, applied to cookies, and left to harden, it morphs into a work of art.
I never use meringue powder for anything other than icing, where the proportion of sugar to meringue is so high that no additional flavoring is needed. However, if you use meringue powder in chocolate buttercream or coconut cream pie or buttermilk cupcakes, you likely will want to add some pure vanilla extract or other flavoring to moderate the slight cornstarch aftertaste.
If you're planning to give your baked goods to a shelter or food pantry, it's good to know that meringue powder is gluten free, safe from salmonella, and some brands are certified kosher. Meringue powder has a long shelf life (up to two years), as long as it's kept dry and not contaminated by dipping a wet or used spoon -- or icing-covered finger -- into it.
Can you substitute powdered egg whites for meringue powder? Absolutely. Can meringue powder be substituted for powdered egg whites? Yes, in recipes that call for beaten egg whites.
Drop In & Decorate royal icing
This recipe makes icing that's fluid enough to flow through the tip of a pastry bag, yet hardens overnight to a perfect and delicious coating. If you don't know how to use a pastry bag, ask for a quick lesson at your local bakery. It’s easy; we’ve had children as young as age 3 decorate cookies with pastry bags. Makes 2-1/2 cups, enough for one batch of cookies.
1 lb + scant 1/4 cup confectioners sugar
5 Tbsp meringue powder
1/2 cup cool water (add more, a teaspoon at a time, if needed for desired consistency)
A few drops of paste food coloring
In the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl with a hand mixer, combine first three ingredients and mix on low speed until glossy and fluffy, 7-8 minutes. To color, place some icing in a small bowl or plastic cup, and stir in a few drops of food coloring until desired shade is reached. Royal Icing hardens quickly when exposed to air, so use immediately, or transfer to an airtight container; it will keep overnight at room temperature. Beat well before using.
*Production note: If you're doing multiple batches of dough, you'll need more icing. An easy way to do this efficiently is to make the icing, one batch at a time, and pour into an airtight container. Make several batches of icing. Then, using a ladle or 1/2 cup measure, place a small bit of the icing in a plastic cup. Mix in food coloring to desired shade, and fill a pastry bag. Repeat until you have all the colors you need. To keep the icing from hardening, place bags tip down in a bowl that has a damp paper towel in the bottom.
**Remember, place the decorated cookies on a tray and leave out overnight, uncovered, to harden. The next morning, package in food-safe cellophane bags or cookie tins.
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