Upside Down Lemon-Blueberry Sheet Cake
makes 2 quarter-sheet pans of cake
Lemon sheet cake ingredients:
230g or 2 sticks unsalted butter, softened
625g or 3 cups plus 2 Tbl sugar
4 large eggs
4 large egg yolks
220g or 1 cup buttermilk
120g or ½ cup plus 2 Tbl neutral oil
460g or 4 cups cake flour
1 Tbl baking powder
2 tsp kosher salt
145g or ½ cup plus ½ Tbl lemon juice
Lemon sheet cake directions:
Heat the oven to 350°F. Bake for 30-35 minutes.
Pan-spray two quarter-sheet pans and line them with parchment paper, or just line the pans with silicone baking mats.
Combine the butter and sugar in the bowl of a stand mixer fitted with the paddle attachment and cream together on medium-high for 2 to 3 minutes, until light and fluffy. Scrape down the sides of the bowl halfway through this process, and again at the end of it. Add the whole eggs and egg yolks, one at a time, beating on medium-high for 1 minute after each addition. After the last addition, scrape down the sides of the bowl, then beat on high for 4 more minutes. Scrape down the sides of the bowl again.
Combine the buttermilk and oil, and with the mixer on medium speed, stream them into the batter very slowly. It should take approximately 3 minutes to add these liquids. Scrape down the sides of the bowl, increase the mixer speed to medium-high, and paddle for an additional 2 to 3 minutes, until the mixture is practically white, twice the size of your original fluffy butter-and-sugar mixture, and completely homogeneous. Don’t rush the process. You’re basically forcing too much liquid into an already fatty mixture that doesn’t want to make room for that liquid.
There should be no streaks of fat or liquid. Stop the mixer and scrape down the sides of the bowl. Whisk together cake flour, baking powder, and salt in a medium bowl. With the mixer on very low speed, slowly add the dry mixture and mix for 45 to 60 seconds, just until your batter comes together. Scrape down the sides of the bowl, then mix on low for an additional 45 seconds to make sure no lumps of cake flour get left behind. Stream in the lemon juice and mix on low until it is fully incorporated.
Divide the batter evenly between the quarter-sheet pans and, using a spatula, spread the cake batter into even layers. Bake for 30 to 35 minutes, rotating the pans front to bake halfway through baking. The cakes will rise and puff, doubling in size, but will remain slightly buttery and dense.
At 30 minutes, gently poke the edge of each cake with your finger: The cakes should bounce back slightly and the centers should no longer be jiggly. If they don’t pass these tests, leave the cakes in the oven for an additional 3 to 5 minutes. Let the cakes cool in the pans on a wire rack or, in a pinch, in the fridge or freezer (don’t worry, it’s not cheating). The cooled cakes can be stored in the fridge, wrapped in plastic wrap, for up to 5 days.
Milk soak
Ingredients:
110g or ½ cup whole milk
1 tsp vanilla extract
Directions:
Whisk together the milk and vanilla in a small bowl. Set aside.
Citrus Milk Crumbs
makes about 250g (2 cups)
Ingredients:
40g or ½ cup milk powder
40g or ¼ cup all-purpose flour
25g sugar
2 Tbl cornstarch
½ tsp kosher salt
¼ tsp citric acid
55g or ½ stick unsalted butter, melted
20g or ¼ cup milk powder
90g or 3 oz white chocolate, melted
Directions:
Heat the oven to 250°F. Line a sheetpan with parchment paper.
Combine the milk powder, the flour, sugar, cornstarch, salt, and citric acid in a medium bowl. Toss to mix. Add the melted butter and toss, using a spatula, until the mixture starts to come together and form small clusters.
Spread the clusters on the lined sheet pan and bake for 20 minutes. The crumbs should be sandy at that point, and your kitchen should smell like buttery heaven. Cool the crumbs completely.
Crumble any milk crumb clusters that are larger than ½ inch in diameter and put the crumbs in a medium bowl. Add the 20g (¼ cup) milk powder and toss together until it is evenly distributed throughout the mixture.
Pour the white chocolate over the crumbs and toss until your clusters are enrobed. Then continue tossing them every 5 minutes until the white chocolate hardens and the clusters are no longer sticky. The crumbs will keep in an airtight container in the fridge or freezer for up to 1 month.
Jammy Blueberry Sauce
makes about 400g (2 cups)
ingredients:
1½ tsp cornstarch
1½ tsp water
2 Tbl lemon
340g or 12 oz blueberries
50g or ¼ cup sugar
⅛ tsp kosher salt
Directions:
Mix together the cornstarch and water to make a slurry.
Put the lemon juice into a small saucepan and add the slurry, blueberries, sugar, and salt. Bring everything to a boil over medium heat. Reduce the heat to low and continue cooking until the blueberries
blister and the mixture turns dark blue, 5 to 6 minutes. The blueberries should still maintain their shape and not break down completely.
Cool the sauce before using. The sauce will keep in the refrigerator, in an airtight container, for up to 2 weeks.
Lemon Frosting
makes about 990g (4 cups)
Ingredients:
330g or 3 sticks unsalted butter, softened
620g or 5¼ cups confectioners’ sugar
1½ tsp kosher salt
Zest of 2 lemons
60g or ¼ cup lemon juice
Directions:
Add the butter to the bowl of a stand mixer fitted with the paddle attachment and cream it on medium-high for 2 to 3 minutes, until the mixture is smooth and fluffy. Scrape down the sides of the bowl.
Add the confectioners’ sugar and salt and mix on low speed just to incorporate them. Crank the speed back up to medium-high and beat for 2 to 3 minutes, until you have a beautifully smooth frosting.
Use a Microplane to zest the lemons. Do your best to grate only as far down as the yellow part of the skin; the white pith has less lemon flavor and can be bitter.
Slowly stream lemon juice, along with the zest, into the frosting with the mixer on low speed. Once the zest and juice are incorporated, crank up the mixer once more and beat the lemon frosting for 1 more minute.
Use the frosting immediately or store it in an airtight container in the fridge for up to 1 week. If you store it in the refrigerator, be sure to loosen it up before using, otherwise it will be impossible to spread. The easiest way to do this is by putting the frosting in the bowl of a stand mixer fitted with the paddle attachment and beating it on medium speed for 3 to 4 minutes.
Cake assembly instructions:
Put a piece of parchment paper on the counter. Run a knife or offset spatula along the edges of one of the quarter-sheet pans of cake to loosen it from the pan, then invert that cake onto it and peel off the parchment from the bottom of the cake.
layer 1, the bottom
Clean the quarter-sheet pan and line it with clean parchment paper Place the cake back inside the pan.
Dunk a pastry brush in the milk and give the cake a good, healthy bath with the milk.
With an off-set spatula, spread one-half of the lemon frosting in an even layer over the cake.
Sprinkle half of the citrus milk crumbs evenly over the lemon frosting. Use your hand to press them lightly into the frosting, anchoring them in place. Then spread the blueberry jam as evenly as possible over the crumbs.
layer 2, the top
Run a knife or offset spatula along the edges of the second quarter-sheet pan of cake to loosen it from the pan, then invert that cake directly on top of the blueberry jam layer. Peel off the parchment from the bottom of the cake and cover it with the remaining frosting. Smooth for a perfectly flat top.
Garnish the frosting with the remaining citrus milk crumbs.
Transfer the cake to the freezer and freeze for a minimum of 12 hours to set the cake and filling. Once set, if not serving right away, wrap in plastic and freeze for up to 2 weeks.
At least 3 hours before you are ready to serve the cake, pull it out of the freezer and, using an offset spatula or a bench scraper, pop the cake out of the pan.
Transfer the cake to a cutting board and fill a pitcher with hot water and set it aside. Use a chef’s knife to trim the edges of the cake so you are left with flush, smooth sides, submerging the knife in hot water between cuts and wiping the blade clean. This makes for crumb-free, professional-looking cuts every time!
Place the cake on a large, rectangular platter. Let it defrost in the fridge for a minimum of 3 hours. (Wrapped well in plastic, the cake can be refrigerated for up to 5 days.)
Cut into squares to serve.