Egg White Chocolate Cake
A fudgy, moist two-layer chocolate cake made with egg whites and sour cream, frosted with a silky chocolate Swiss meringue buttercream. A great recipe for using up leftover egg whites.
Ingredients
Cake
- 190 g all-purpose flour
- 50 g natural cocoa powder
- 1 1/2 teaspoon baking soda
- 1/2 teaspoon baking powder
- 3/4 teaspoon salt
- 3 large egg whites
- 150 g granulated sugar
- 100 g soft brown sugar
- 120 g sour cream room temperature
- 120 g whole milk room temperature
- 55 g oil (vegetable or melted coconut oil)
- 1 teaspoon apple cider vinegar or white vinegar or lemon juice
- 1 teaspoon vanilla paste or extract
- 180 g hot coffee or use hot water
Chocolate Swiss Meringue Buttercream
- 230 g semi-sweet chocolate
- 4 large egg whites
- 150 g granulated sugar
- 340 g unsalted butter softened to room temperature
- 1 teaspoon vanilla paste
- 1/4 teaspoon salt
Instructions
Cake
- Preheat the oven to 350°F (180°C). Grease and line two 8-inch round cake pans with parchment paper.
- In a bowl, whisk together the flour, cocoa powder, baking soda, baking powder, and salt. Set aside. 190 g all-purpose flour, 50 g natural cocoa powder, 1 1/2 teaspoon baking soda, 1/2 teaspoon baking powder, 3/4 teaspoon salt
- In a separate large bowl, whisk together the egg whites, sugars, sour cream, milk, oil, vinegar, and vanilla until combined. 3 large egg whites, 150 g granulated sugar, 100 g soft brown sugar, 120 g sour cream, 120 g whole milk, 55 g oil, 1 teaspoon apple cider vinegar, 1 teaspoon vanilla paste
- Add half the dry ingredients to the wet ingredients and mix. Pour in the hot coffee along with the remaining dry ingredients and mix until just combined. Do not overmix. 180 g hot coffee
- Divide the batter evenly between the prepared pans. Bake for approximately 25 minutes, until a skewer inserted into the center comes out clean.
- Run a knife around the edges of each cake to loosen. Let them sit in their pans for 15 minutes, then carefully turn out onto a wire rack. Cool completely, about 1 hour, before frosting.
Chocolate Swiss Meringue Buttercream
- Melt the chocolate in a microwave-safe bowl in 20 to 30 second bursts, stirring after each, until fully melted. Set aside to cool to room temperature. 230 g semi-sweet chocolate
- In a clean, grease-free metal bowl (either the bowl of your stand mixer or another metal bowl) combine the egg whites and granulated sugar. Set the bowl over a pot with 1 inch of gently simmering water, making sure the bottom of the bowl does not touch the water. Do not use a glass or ceramic bowl as it can crack or shatter. Whisk constantly until all the sugar has dissolved and the mixture reaches 160°F (71°C) on an instant-read thermometer. 4 large egg whites, 150 g granulated sugar
- If you heated the egg whites in a separate metal bowl, transfer the mixture to the bowl of your stand mixer now. Fit the stand mixer with the whisk attachment and beat on medium-high speed until stiff, glossy peaks form and the bowl is completely cool to the touch, about 8 to 10 minutes.
- With the mixer running on medium speed, add the softened butter one cube at a time, waiting until each cube is fully incorporated before adding the next. The mixture may look curdled at this stage. Keep beating and it will come together into a smooth, fluffy buttercream. 340 g unsalted butter
- Beat in the cooled melted chocolate, vanilla, and salt until fully incorporated and the buttercream is thick and fluffy. 1 teaspoon vanilla paste, 1/4 teaspoon salt
- Switch to the paddle attachment and beat on low speed for 10 minutes to remove the larger air bubbles.
Assemble
- Place one cake layer on a serving plate or cake board. Spread a generous layer of buttercream over the top. Place the second layer on top and frost the top and sides as desired.
Notes
- Room temperature ingredients: Sour cream, milk, and egg whites should all be at room temperature for the smoothest batter.
- Natural vs. Dutch-processed cocoa: Natural cocoa gives a deeper flavor here and works better with the baking soda. Dutch-processed will also work.
- Coffee: Substitute hot water if preferred. The cake won't taste like coffee either way.
- Curdled buttercream: Keep beating, it will come back together. If it looks soupy, refrigerate for 10 minutes then re-whip.
- Storage: Room temperature up to 2 days, refrigerated up to 4 days. Cake layers and buttercream both freeze well for up to 3 months.
- Both metric and US customary measurements are provided. Use the toggle to switch between the two.
Nutrition
Serving: 1sliceCalories: 690kcalCarbohydrates: 68gProtein: 6gFat: 45gSaturated Fat: 24gPolyunsaturated Fat: 3gMonounsaturated Fat: 14gTrans Fat: 1gCholesterol: 83mgSodium: 458mgPotassium: 228mgFiber: 2gSugar: 50gVitamin A: 955IUVitamin C: 0.1mgCalcium: 74mgIron: 2mg
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