Recently, when testing a crumb cake recipe, I started to wonder how to make a more reliable streusel topping. Even before sprinkling the crumbly mix of brown sugar, butter, and other flavorings over the batter, I could tell that, once baked and sliced, the topping wasn’t going to hold together.
Call it a crisp or call it a crumble—whatever you call it, you're going to be making it all summer long.
The same thing happens whenever I make coffee-cake muffins. When I take a bite—or sometimes even before the bite, when the muffins are first turned out of the pan—the nuts and brown sugar and buttery nubbins fly away to the floor, never to be eaten, never enjoyed.
I thought about adding more butter, but knew that would only make the streusel too heavy—the crumbly mass would likely sink into the batter. More brown sugar? That'd make it too sweet. So I reached for egg whites instead.
As my Epi colleague Anna Stockwell writes in her method for easy No-Recipe-Required Granola, egg whites have the power to help ingredients clump together. And since they’re light, I knew they wouldn’t weigh down that streusel. The result was a crisp topping that sliced beautifully and stayed intact.
My Epi colleagues and I decided to try the experiment again, this time with a plum-layered coffee cake. We baked one control cake, prepared and baked as per the recipe; and one cake with 1 large egg white added to the crumb topping (and no other adjustments).
The result was a happy afternoon of cake eating among the Epi staff. (Seriously, this cake is fantastic.)
As for the crumb toppings: the egg white–enriched one was noticeably glossier and a shade darker than the topping on the control cake. When we cut into the cakes, the control cake sliced more easily, since the crumb topping provided no resistance. However, the crumbs scattered about the cutting board—not completely, but enough to notice. The crumb topping with egg white, on the other hand, practically formed a shell, so cutting through it took just the slightest bit more force. In addition, that topping was decidedly more crunchy—a characteristic the Epi team was split on. The topping with egg whites did cling more tightly to the cake, leaving fewer stray crumbs along its perimeter.
Here's how to make your own crunchy streusel topping:
1. Choose a recipe
Take any coffee cake, crumb cake, or other streusel-topped recipe you'd like to improve. Here are a few of our favorites.
2. Combine topping
Mix crumble or streusel by hand or via food processor as your recipe instructs.
3. Add egg whites
By hand, combine approximately 2 cups topping with 1 large egg white and stir to combine.
3. Proceed with recipe as written.
You'll be rewarded with a glossy, crunchy topping—and, of course, no more fly-away nubbins.