Every baker has a box of confectioners' sugar in the pantry, but only a few actually use it for baking. When making cookies or cakes, we're more likely to reach for granulated or brown sugar, saving the confectioners' sugar for dusting over brownies or making a quick glaze.
This division of labor makes perfect sense. Confectioners' sugar (also known as powdered sugar, icing sugar and 10X sugar) is granulated sugar that's been ground into a fine powder and then cut with a small amount of cornstarch (about 3 percent) to prevent lumpiness and crystallization. It dissolves almost instantly when combined with butter or water, for the silkiest buttercreams and shiniest icings. As a bonus, the small amount of cornstarch gives frostings and icings a little body. In these capacities, a little confectioners' sugar goes a long way, which is a good thing, since it is about twice as expensive by weight as granulated sugar.
But if money is no object, there are times when confectioners' sugar can be used in, and not just on, baked goods. After all, it is 97 percent granulated sugar. And since it contains cornstarch, an ingredient often added to baked goods to tenderize them, it might be especially good in recipes where a soft and yielding texture is desirable.
It is perfect in Scottish shortbread, where a sandy, melt-in-your-mouth texture is the goal. Confectioners' sugar combines easily with butter for a crumbly rather than crisp cookie. The cornstarch in confectioners' sugar contributes to the cookies' softness.
Likewise, fine and crumbly Mexican wedding cakes and Russian tea cakes (which are, after all, a kind of shortbread dough with ground nuts) are good candidates for this substitution.
Less obvious but worth a try are madeleines. When I make these little French cakes with granulated sugar, I get a coarse crumb resembling cornbread. With confectioners' sugar, the cakes' texture is finer and lighter, more like a buttery spongecake.
If you want to give confectioners' sugar a try in a favorite recipe, swap 1 3/4 cups of confectioners' sugar for every cup of granulated sugar.
CONFECTIONERS' SUGAR POUND CAKE
Creaming together butter and confectioners' sugar can be quite a messy business. To prevent a cloud of sugar from rising and raining sugar dust over every surface of your kitchen, drape a large kitchen towel over your standing mixer and bowl before you turn on the mixer. Orange zest and marmalade can be substituted for the grapefruit, or you can leave them out for a vanilla version of this tender pound cake.
4 large eggs
2 teaspoons pure vanilla extract
1 1/2 cups unbleached all-purpose flour
3/4 teaspoon baking powder
1/4 teaspoon salt
1 cup (2 sticks) unsalted butter, softened
2 teaspoons grated grapefruit zest (optional)
2 1/3 cups confectioners' sugar
2/3 cup grapefruit marmalade (optional)
1. Preheat oven to 325 degrees. Coat inside of a 9-by-5-inch loaf pan with nonstick cooking spray and dust with flour, knocking out any extra flour.
2. Combine eggs and vanilla in a glass measuring cup and lightly beat. Combine flour, baking powder and salt in a medium mixing bowl.
3. Place butter and grapefruit zest, if using, in a large mixing bowl and beat on low speed. Add confectioners' sugar, 1/2 cup at a time, until incorporated, scraping down sides of bowl after each addition. Turn mixer to medium-high and cream until fluffy, about 3 minutes.
4. With mixer on medium-low, pour egg mixture into bowl in a slow stream, stopping mixer once or twice to scrape down sides.
5. Turn mixer to low and add flour mixture, 1/2 cup at a time, scraping down sides of bowl after each addition. After last addition, mix for 30 seconds on medium speed.
6. Scrape batter into prepared pan and smooth top with a rubber spatula. Bake until cake is golden and a toothpick inserted in center comes out clean, about 1 hour and 15 minutes. Let cake cool in pan for 5 minutes, invert onto a wire rack, turn right-side up on rack and let cool completely.
7. Heat marmalade, if desired, in a small pot over medium heat until liquid. (Alternatively, place in a microwave-safe bowl and microwave 10 to 30 seconds, until liquid.) Brush top of cake with marmalade. Slice and serve.