Full Sheet Cakes Recipe

Preheat and prepare pan

Preheat oven to 350°F (175°C). Grease a full sheet pan (18 x 26 in) and line with parchment paper; grease parchment as well for easy release.

Combine dry ingredients

In a very large mixing bowl (or in batches), whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, and sea salt until evenly distributed.

Cream butter, oil, eggs and vanilla

In the bowl of a heavy-duty stand mixer fitted with the paddle attachment, add softened unsalted butter and vegetable oil. Beat on medium-high until smooth and slightly pale, about 2–3 minutes. Add eggs one at a time, mixing 15–20 seconds after each addition until incorporated. Add vanilla extract and mix until combined.

Alternate add milk and dry ingredients

With the mixer on low, add roughly one-third of the dry ingredients and mix until just incorporated. Add half the milk, mix, then another third of the dry ingredients, the remaining milk, and finish with the remaining dry ingredients. Scrape the bowl often and mix only until a smooth, homogenous batter forms—do not overmix.

Adjust consistency and fill pan

Batter should be pourable but not thin—if too thick add up to 1/2 cup more milk. Pour the batter into the prepared full sheet pan and smooth the top with an offset spatula or back of a spoon to an even thickness.

Bake

Bake in the preheated oven for 20–28 minutes, checking from 18 minutes onward. Because sheet-pan depths vary, test by inserting a toothpick or skewer in several places — it should come out with a few moist crumbs but not raw batter. Rotate the pan halfway through baking if your oven has hotspots.

Cool

Remove the pan from the oven and place on a wire rack. Let the cake cool in the pan 10–15 minutes to set, then run a thin spatula around edges and invert onto a large cooling rack. Peel off parchment and allow cake to cool completely (at least 1 hour) before syruping and frosting.

Combine water and sugar in a small saucepan over medium heat. Stir until sugar dissolves, then bring to a gentle simmer for 1–2 minutes. Remove from heat and stir in vanilla extract. Cool to warm (not hot) before using. Brush or gently pour the syrup evenly over the cooled cake (about 1–1½ cups total or to taste) to moisten; allow it to absorb for 10–15 minutes.

Make sugar syrup for meringue

Combine the granulated sugar and 1 cup water in the heatproof bowl of a stand mixer (or a metal bowl). Whisk until combined.

Heat and whisk egg whites

Add the egg whites to the sugar bowl and place the bowl over a pot of simmering water (double-boiler) making sure the bowl bottom doesn't touch the water. Whisk constantly until the sugar dissolves and the mixture reaches 160°F (71°C) on an instant-read thermometer, and mixture feels warm to the touch (about 3–5 minutes).

Whip meringue to stiff peaks

Transfer bowl to the stand mixer fitted with the whisk attachment. Whip on high until the mixture is glossy, thick and has cooled to near room temperature (about 8–12 minutes).

Add butter

With the mixer on medium, add the softened cubed butter a few pieces at a time, allowing each addition to incorporate before adding more. If the mixture appears curdled at any point, continue beating — it should come back together as it warms. Once all butter is added and the buttercream is smooth, add vanilla extract and salt; mix to combine.

Adjust texture

If buttercream is too soft, chill briefly (10–20 minutes) then re-whip. If too firm, beat at medium speed to warm slightly. Color portions as desired with gel coloring.

Frost cake

Place the cooled, syrup-brushed cake on a flat board or serving tray. Using an offset spatula, apply a thin crumb coat of buttercream and chill 15–20 minutes to set. Apply a final even layer of buttercream to desired thickness, smooth with a bench scraper or spatula. Reserve some buttercream for piping details if desired.

Tint reserved buttercream with gel colors as desired. Transfer to piping bags fitted with tips for borders, rosettes, or lettering. Apply sprinkles or other decorations. Chill the finished cake 15–30 minutes so decorations set before transport or serving.