White Zucchini Cake with Whipped Vanilla Frosting, Lemon Curd and Blueberries

It has never occurred to me to make a White Zucchini Cake…

I’d always made zucchini cake as a chocolate cake and reserved non-chocolate zucchini flavors for breads and muffins. I’m sure it had something to do with camouflaging those green flecks within a deep dark chocolate cake so that no one would be the wiser. At least that was going philosophy when I was young and “zucchini cake” sounded like an oxymoron.

When I saw this recipe from Amanda at I am baker, I was so intrigued that I needed to try it right away. Then I saw her Blueberry Zucchini Cake and I knew I had to make some type of one of these versions.  I hadn’t intended to blog about it; I really just wanted to try it out and see what this whole White Zucchini Cake was all about. So I started with the recipe for the White Zucchini Cake and used the flavors from the Blueberry Zucchini Cake.

The first thing I noticed about the White Zucchini Cake recipe was that I would have three egg yolks left over. Three egg yolks always become fresh lemon curd in my house. Always. Amanda frosted her cake with chocolate frosting and topped it with fresh blueberries which I thought was a delicious combination, but since I knew I’d be making lemon curd and wanted to use it for the cake, I replaced the chocolate frosting with a Whipped Vanilla Frosting.

The frosting deserves a post of its own, but since I hadn’t decided to blog about any of this until after I baked the cake, I didn’t shoot any of the frosting making process. For those of you who have read the Whipped Cream Cream Cheese Frosting post or the Whipped Chocolate Frosting post, you know I am not a huge fan of frosting that is too sugary or too buttery. This Whipped Vanilla Frosting is the vanilla version of the Whipped Chocolate Frosting and it is another wonderful, not too sweet, not too buttery frosting. #howtooverusethewordfrosting

It’s a cooked flour frosting. It starts with cooking a flour and milk mixture until it becomes a thick paste. It smells exactly like Cream of Wheat while it’s cooking, but since you’re using flour, there are no grains, just a thick, smooth paste. Then you’ll whip up your butter, sugar, vanilla and salt, add the cooled paste and whip until you end up with a beautiful, light, fluffy frosting that will not send you into a sugar coma. It’s not complicated and the results are wonderful. It’s a perfect choice for this cake.

Okay. Back to the cake. The original recipe uses a yellow zucchini to keep the cake as white as possible.  I had green zucchini and didn’t want to peel it. I thought the green flecks would be beautiful with the yellow lemon curd and the deep indigo berries. And since I didn’t need to hide the fact that the cake had zucchini in it, I went green and never looked back.

I had no idea what the texture of this cake would be like but I wanted to try to make it as fluffy as possible, so instead of just mixing in the egg whites, I whipped them up and folded them into the batter. The cakes didn’t rise as high as I had hoped, but they were cooked perfectly so I moved on. (As you can see from the photos, they layered up to be plenty tall.)

I had already decided I wasn’t going to frost the sides of the cake, so I started with a simple assembly. I took one of the cakes and spread some frosting evenly into a circle, leaving some room at the edge. I topped that with a layer of lemon curd and then completely covered the curd with a layer of blueberries. I wanted to insure that the berries stayed put, so I frosted the bottom of the top cake layer and pressed it on the berries which very effectively sandwiched them between the cake layers.

I repeated the frosting and lemon curd on the top and had intended to cover the entire top with berries, mimicking the layer I had just completed, but the lemon curd looked so pretty framed by the berries that I decided to go with a simple double row and stop there. (I had forgotten that Amanda had also done the same thing until I was setting up the links back to her post and then realized where that “inspiration” had come from :)

The combination of flavors was perfect. The cake is not super sugary sweet, so it balances well with the sweetness of the frosting and the sweet/tart lemon curd. The blueberries are the proverbial icing on top of the cake and add wonderful flavor and freshness. The cake itself has a texture that’s a little hard to describe. It’s not fluffy like a traditional white cake and yet it doesn’t have the texture of zucchini bread or muffins. It’s moist and dense and yet still has somewhat of a cake texture.

White Zucchini Cake with Whipped Vanilla Frosting, Lemon Curd and Blueberries. After I made the frosting and lemon curd, I thought I should take some photos, just in case it came out really good. Because if it was good, of course, I would want to tell you all about it. All I can say is that everyone (kids and adults) thoroughly enjoyed it…

green flecks and all :)

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White Zucchini Cake with Lemon Curd, Buttercream and Blueberries

Ingredients

For the cake:

• 2 cups cake flour I used unbleached from King Arthur Flour
• 3 teaspoons baking powder
• 1/2 teaspoon salt
• 1/2 cup 1 stick unsalted butter, room temperature
• 2/3 cup sugar
• 1/2 teaspoon vanilla
• 2/3 cup milk I used whole milk
• 1 cup drained and squeezed, finely shredded zucchini
• 3 large egg whites reserve yolks for lemon curd

For the frosting :

• 3 Tablespoons all purpose flour
• 1 cup milk I used whole milk
• 1 cup 2 sticks unsalted butter, cool room temperature
• 1 cup sugar
• 1 teaspoon vanilla
• 1/4 teaspoon salt

For the lemon curd:

• 3 large egg yolks
• 1 teaspoon lemon zest
• 1/4 cup fresh lemon juice
• 6 Tablespoons sugar
• 4 Tablespoons unsalted butter cold, cut into pieces
• Fresh blueberries about 2 cups, depending upon how you garnish the top, washed and dried

Instructions

1. Make the lemon curd in advance, so that it has time to cool.
2. For the curd, combine yolks, zest, juice and sugar in a small saucepan.
3. Whisk to combine. Set over medium heat and stir constantly, making sure to scrape sides and bottom of pan.
4. Cook until mixture is thick enough to coat the back of a spoon, about 5-7 minutes.
5. Remove from heat. Add butter, one piece at a time, stirring until consistency is smooth.
6. Transfer the mixture to a medium bowl. Lay a sheet of plastic wrap directly on the surface to prevent a skin forming. Allow to cool then refrigerate. You can speed up this process by placing the bowl with the lemon curd in it into a larger bowl filled with ice. This recipe makes about 3/4 of a cup of lemon curd.
7. Make the cake. Preheat the oven to 350 degrees F. Spray two 8" pans with baking spray, line the bottoms with parchment, then lightly spray the parchment. Set aside.
8. Sift together cake flour, baking powder and salt. Set aside.
9. In a mixer with paddle attachment, combine butter, sugar and vanilla. Beat on low until fully combined then on high for another 3-4 minutes until light and fluffy.
10. Alternate adding flour mixture and milk to butter mixture, beginning and ending with flour mixture (1/3 of the flour, 1/2 milk, 1/3 of flour, 1/2 of the milk, 1/3 of the flour mixture)
11. Fold in shredded zucchini until fully combined.
12. Beat egg whites to stiff peaks, then fold into batter until no streaks of egg white remain.
13. Divide batter evenly between prepared pans and bake for 25-30 minutes or until toothpick comes out clean. My cakes took about 25-27 minutes.
14. Remove from oven and allow to cool in pans for about 10 minutes, then remove from pans and finish cooling on racks.
15. Make the cooked flour portion of your buttercream. Place the 3 Tablespoons of flour into a small sauce pan and place over medium low heat. Whisk in 1/4 cup of the milk insuring that all flour gets incorporated and you don't have lumps. You're creating a slurry. Slowly whisk in the remaining milk. Adding small amounts of liquid at a time will help you avoid any lump issues. Continue to whisk over the heat and continue whisking for 1 minute after the mixture begins to boil. Remove from heat. Transfer to a shallow dish to allow for faster cooling. Press a piece of plastic wrap on the surface to deter a skin from forming. Allow to cool at room temperature until it's just barely warm, then transfer to the refrigerator. It will become a soft solid mixture once it is cooled.
16. When the cakes are fully cooled and you are ready to frost your cake, make your frosting.
17. With a mixer, beat the two sticks of butter,vanilla and sugar until well combined and fluffy about 1-2 minutes. Slowly add spoonfuls of the cooled cooked flour mixture into the butter mixing well after each addition. After all of the cooked flour mixture has been added, continue beating the mixture until it is light and fluffy and the sugar is completely dissolved (check by rubbing some frosting between your fingers.) If the mixture looks curdled, it isn't done yet. Just keep mixing it until it all comes together.
18. To assemble cake, spread a little less than half of the frosting on top of your first layer staying about a half inch in from the cake edge. Spread half of the lemon curd on top of the frosting layer leaving a half inch to an inch from the frosting edge. Press a layer of fresh blueberries on top of the lemon curd. I fully covered the lemon curd with blueberries.
19. Spread a layer of frosting on the bottom side of the top cake layer, flip it over and press it on top of the blueberries so that the blueberries are sandwiched between the two layers of cake with frosting and lemon curd beneath them and just frosting above them.
20. Repeat the frosting and lemon curd layers on top of the cake, then press blueberries into the lemon curd. You can create a circular design as I have, or cover the entire top with berries.

Recipe Notes

*Store cake in refrigerator, but allow to come to room temperature for serving for best flavor and texture.

*You can make the cooked flour portion of the frosting further in advance. In the recipe, I planned time for you to make it while the cake is baking and cooling. I actually made mine in the morning and stored in the refrigerator until I needed it later that afternoon.

White Zucchini Cake slightly adapted from Iambaker

Whipped Vanilla Frosting adapted from Our Best Bites Lemon Curd Recipe from Martha Stewart

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