So you’ve got a special occasion coming up, and you want to/need to/are being made to bake a fabulous cake to celebrate. Your heart says “impressive layer cake!” but your pantry reminds you that you didn’t miraculously sprout a collection of variously-sized cake pans overnight. (It’s ok, leave the hoarding to the professionals.) I’m here to remind you that you can make a super-snazzy, not to mention delicious, layer cake using just a baking sheet + a little know-how.
Lovers of traditional sheet cakes can attest: In a pinch, there’s nothing better. These cakes are easy to bake and topped with a fat, swirly layer of decadent frosting, so everyone is sure to love them. But why not dress up the classic sheet cake? In just a few steps you can turn a simple slab o’ cake into a majestic tower of cake greatness. But before you dive in fork first, here’s what you need to know.
This first step is pretty easy: Pick your cake recipe. If it’s not a sheet cake recipe, you can check out this brilliant guide to help you determine how to increase/decrease the recipe to fit into a sheet pan. Start by looking through your baking pans and choosing a sturdy one, preferably one with at least 1-inch tall sides and a nice, flat base. Grease the baking sheet with nonstick spray and line with parchment paper, then grease the parchment paper. If your recipe says to grease + flour the pan, don’t skip that step just because it’s a sheet pan, as it will make it much easier to remove the cake later! Pour your batter into the prepared pan and smooth it into an even layer (as much as you can), using a spatula.
Remember that the type of cake you’re using is important, and flavor isn’t the only factor. Really dense cakes (think pound cake) can be heavy and therefore difficult to stack—the filling can smoosh out of the center (no good). Overly delicate cakes or very thin layers can be difficult to cut and layer in one piece. When I make these cakes, I keep them simple and two-layered. I just take one single sheet cake and cut it in half to create the two layers. If you want to go bold, you can absolutely make two full sheet cakes and stack them together. I believe in you and that awesome, gigantic cake you’re building. Go for it!
For some layer cakes, the “filling” is just the frosting—used on both the inside and the outside of the cake (that’s delicious enough). But for many layer cakes, there is a different filling in between the cake layers, providing flavor, color, and textural contrast inside the cake. There can even be more than one filling. Sometimes, I’ll pipe one filling around the outer edge (fluffy buttercream), then fill the center with something else (like lemon curd). Fillings can be as simple as purchased jam or preserves, and as complicated as additional recipes (pastry cream! ganache! caramel!).
Inclusions are items added in addition to fillings (chocolate chips/chunks/shavings, crushed candy, chopped nuts, sliced fresh fruit, and so on), usually as a separate layer. They are totally optional, but break up the softness of layer cakes in a nice way. Remember that when you use inclusions, they can create structural concerns; fresh fruit, for example, contains a lot of moisture, so it can make a slippery surface for adding the next layer. To combat this, you can gently press the inclusions into the filling below to help them adhere, and be extra careful with slippery fillings like jam or curd. You can also spread a small layer of filling, place the inclusions on top, then apply more filling on top of the inclusions. That way, the next cake layer is still resting on filling rather than the inclusion. Also be mindful of how inclusions can play into slicing the finished cake; keep pieces small enough that they won’t impede the knife or fork later.
Chooose Your Frosting
The frosting can be nearly any kind you like. The main consideration is the look you’re hoping for in the exterior; some frostings, like Italian buttercream, are silky smooth and thus achieve a clean, sleek look. Other frostings (pudding-style or American buttercream) are a little thicker and, while they can still be manipulated into lots of looks, might be a little bit more trouble. (If you’re looking for a swirly, rustic look, they’ll be perfect.) I used to prefer my frosting on the firmer side, because it was easier to work with, but a wonderful pastry chef friend of mine told me that the ideal texture of frosting for decorating a cake was “like mayonnaise.” But as soon as I tried her tip, I was hooked: Soft frosting spreads beautifully, whether you’re making gorgeous swirls or sharp edges. Other frostings I like to use are German buttercream, French buttercream, and whipped ganache.
I always find that the edges of my sheet cakes are slightly different heights than the rest of my cake, so I trim the sides and edges away from the cake—just a smidge (about 1/2-inch) to even things off. Also, since there’s no need to level off sheet cakes like you do with a traditional layer cake, these make up for my usual cake scrap snacks.
Cutting the Layers
Normally, cutting cake layers is the first step to strike fear into the home baker. But this couldn’t be easier. Turn your cake out of the pan, but leave the parchment paper attached for now. Use a sharp serrated knife to cut the cake cleanly in half to create two rectangular layers. A standard baking sheet/half sheet pan is about 13 x 18 inches. Cutting in half should create two 13 x 9-inch layers. If your cake is looking particularly wonky, you can try to level it off, but usually sheet cakes bake relatively flat—or at least, flat enough that some extra frosting at the edges can make up the difference. I don’t usually fuss with any sort of leveling. Once cut, most cakes are prone to drying out, so don’t cut your layers too far in advance.
Now, let's discuss stacking the dang thing. You want a layer cake to look symmetrical both before and after slicing. While I usually recommend a cake turntable for round layer cakes, you can assemble and decorate sheet cake layer cakes on whatever you plan to serve them on. Place your first layer on a serving platter. Add your filling to the surface of the first layer, and use an offset spatula to help spread it into an even layer. If you’re using a filling on the looser side, like curd, jam, etc., it’s best to build a sort of retaining wall out of icing first, using whatever you’re planning to frost the outside with. To do so, use a pastry bag to pipe a ring of frosting around the outer edge of the cake layer, then pipe or scoop the filling into the center of the ring and spread into an even layer. If you’re adding inclusions, sprinkle them evenly on top of the filling. When you’re finished applying the filling, place another cake layer on top. Do your best to line up the cake layer at the edges so it’s even and straight. Press the cake layer down gently to make sure it’s really on there. Once the cake is built, I like to refrigerate it for a bit before I begin frosting. This helps the fillings firm up, which makes it easier to decorate. Your carefully built layers can slide if the filling or inclusions are slippery! Thirty minutes usually works for me, and less (or none!) is fine, too—it’s just something that always helps things go smoother for me.
Generally, it’s a good idea to apply a crumb coat. Is it totally necessary? No, not usually, but if you’re going through all of the effort to make a lovely layer cake, it’s worth it: The crumb coat gets rid of any crumbs/cake dust, helps "seal" the whole cake together, and makes smooth sides that are easier to frost later. As a bonus, if your sheet cake wasn’t totally even, and you opted not to level it off (because I told you not to!), a crumb coat can help you add extra frosting anywhere that needs a little extra filler (talkin' about you, tricky corners).
Use an offset spatula to apply frosting to the surface of the cake. Swoop your hand back and forth across the surface of the cake, spread the frosting to the edges. Turn the platter as you work to reach all the sides. To smooth the sides, hold your spatula parallel to the sides, swooping your hand back and forth to ensure even coverage. Once there’s frosting all over, hold the spatula parallel to the cake, straight up and down, and apply gentle pressure as you move across the sides. Once the sides and top are smooth, you can use the offset spatula, held flat just above the surface of the cake, to swipe away the excess “wall” of frosting from the upper edge of the cake. Don’t worry if your cake isn’t frosted perfectly or super-smoothly, though. Decorations can help “cover up” any trouble spots.
Just like regular layer cakes, just about anything goes here. I like to emphasize the rectangular shape by adding a piped border to the base or top edge, or both. This also can help cover up any uneven frosting areas, and who doesn’t love more frosting? Some of my other favorties: adding drizzles or drips to the top and letting it fall to the sides, covering the surface of the cake with fresh fruit, or pressing chopped nuts/coconut/cookie crumbs into the sides to add texture and allude to the flavors inside. This is where you can really dress up your cake and bring out the fancy pants layer cake side to it. (Then again, a sheet cake layer cake is pretty impressive all on its own, sans decoration.)
I always carry three kinds of hot sauce in my purse. I have a soft spot for making people their favorite dessert, especially if it's pie. My first cookbook, The Fearless Baker, is out on October 24, 2017.