I know it may sound a bit weird at first as we usually associate olive oil with savory foods, but trust me, this Blueberry Olive Oil Cake is no weirder than sea salt caramels. It's also a lot easier to make than cakes using butter as it integrates more readily into the batter. The finished cake is marvelously crisp around the edges and ultra-moist and tender on the inside.
Why olive oil
Baking a cake is a delicate interplay of leavening, starch, sugar, and fat. The fat plays many important roles, and for a lighter cake that still has plenty of flavor, the golden-green oil pressed from olives makes for the perfect fat. Here's just some of what it does for the cake:
- Moisture - since fat does not evaporate in the oven, it gives a sense of moistness in the cake even after it's been baked. Most cakes use some form of fat, such as butter, egg yolks, or plain vegetable oil for this reason. In this cake, the olive oil helps ensure the cake doesn't get dry, even after it sits for a few days.
- Texture - Fat is also important in giving cakes their delicate texture. When you add flour and water to a mixture and agitate it, you form an elastic network of gluten. This is what gives doughs their chewy texture. While chewiness is a desirable trait in bread and pasta, it's not a great mouthfeel for cakes, which is where the fat comes in. Fat coats these proteins and impedes the formation of gluten, which is why you can mix this olive oil cake batter without having it turn out like a hockey puck.
- Flavor - Butter is the usual goto when you want to add a rich, creamy flavor to your cake, but olive oil can also have a smooth buttery flavor, which makes it perfect for some cakes. Just be sure to use a mild fruity extra virgin olive oil that you enjoy the taste of. Bitter, astringent or spicy olive oils can make your cake taste unpleasant. I'm using one called Ardoino Fructus, which comes from the Imperia region of Italy.
Flavorings and Fruit
Because the olive oil contributes such a wonderful flavor to this cake, you don't need to do too much in the flavor department. The oil I used has a mild fruity flavor that's round and buttery with just a hint of citrus, which is why I decided to go with a bit of orange zest for the flavoring. Lemon zest, vanilla beans, and cinnamon would all be delightful additions to olive oil cake, and you can add them in with the eggs and sugar.
Texture of the cake
We already touched on the important role that olive oil plays for the texture of the inside of the cake, but what about the outside? I like to give undecorated cakes a nice crust on the outside, so you have something crispy to juxtapose the soft fluffy interior. To do this, I like to line the cake pan with some olive oil and sugar. The oil helps the sugar stick to the side of the pan, while the combination of the two not only prevent the cake from sticking to the pan, they create a sort of caramelized crust that gives your cake a wonderful texture around the edges.
For even more texture, I also sprinkled some very coarse sugar on the bottom of the cake tin. This sugar will not melt completely and gives the bottom of your cake a pleasant crunch as the sugar crystals burst in your mouth.
How to Mix Olive Oil Cake
There aren't a whole lot of ingredients in this cake, but how you combine them will make a big difference in the texture of your finished cake. I borrowed a page from making a French genoise to make this.
First, the eggs and sugar are heated to about 100 degrees F. You don't have to be exact on the temperature; it should be warm, but not hot. Then you whip the mixture into a dense marshmallowy foam that's much more stable than a meringue made with egg whites. The key here is to whip the mix longer than you think it needs to be whipped: 5 minutes is a safe bet.
The foam retains its structure even after incorporating the olive oil and flour, which together with the baking powder gives you some great lift. The resulting batter is viscous enough to hold the blueberries aloft while giving you a beautiful dense crumb that reminds me of a great pound cake.
Once the batter is done, it's just a matter of folding in the berries and popping the cake in the oven until it's cooked through.
Variations of Olive Oil Cake
A blueberry patch near home kept my kitchen stocked with plump, juicy berries this summer, but this olive oil cake is delicious without any berries at all. You can also add other fruit such as chopped up apples, fresh cranberries, blackberries or bananas. Dried fruit such as raisins, currants or blueberries also work well, but I'd recommend rehydrating them in your favorite liquor first.
- 24 grams coarse sugar (such as demerara or turbinado)
- 250 grams all-purpose flour
- 1 teaspoon baking powder
- ½ teaspoon salt
- 4 large eggs
- 200 grams granulated sugar (+ 1 tablespoon for dusting)
- ½ orange (zested)
- 1 cup extra-virgin olive oil (fruity)
- 320 grams blueberries (fresh or frozen)
- Move your oven rack to the middle position and preheat to 350 degrees F (175 C). Find a pot that will comfortably fit your mixer bowl and then bring some water to a simmer in it.
- Drizzle some olive oil into a 9-inch springform pan and then use a paper towel to spread it around the pan evenly. Add about a tablespoon of granulated sugar to the pan and then evenly dust the entire inside surface of the pan, so there are no bare spots. Tap out any excess sugar over the sink. Sprinkle the bottom of the pan evenly with the coarse sugar.
- Add the flour, baking powder and salt together in a bowl and whisk to combine.
- In a heat-safe bowl of an electric mixer, add the eggs and sugar and then add the zest of half an orange into the bowl using a Microplane.
- Turn off the simmering water and then set your mixer bowl in it. Use a whisk to keep the eggs moving so they don't cook and heat the mixture to about 100 degrees F (38 C).
- When the egg mixture is up to the right temperature, attach it to your mixer and fit the mixer with the whisk attachment. Whisk this on high for 5 minutes. The mixture should turn pale yellow and glossy.
- Turn the mixer down to medium speed and then slowly pour in the olive oil until it is fully incorporated.
- Turn the mixer down to low and slowly add the flour mixture until it's just combined (do not overmix).
- Fold in the blueberries by hand with a spatula, and pour the batter into the prepared pan.
- Bake until a toothpick inserted into the center comes out without any liquid batter on it (a few crumbs are okay), about 50-60 minutes.
- Let the olive oil cake cool on a rack for a few minutes before using a knife to separate the cake from the sides of the pan. Let it cool completely before slicing and serving.
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