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–+ servings
angled shot of sliced chocolate mousse cake with another slice beside on stack of two plates, a cake knife and bowl of chocolate curls beside, white flowers and cheese cloth behind.

Dark Chocolate Mousse Cake with Chocolate Mirror Glaze

4.84 from 6 votes
Prep Time: 45 minutes
Cook Time: 1 hour
Refrigeration Time 12 hours
Total Time: 13 hours 45 minutes
Author: Traci Crossland
A chocolate lovers dream cake! With three layers of luscious chocolate, there's really no better dessert than this Dark Chocolate Mousse Cake with Chocolate Mirror Glaze. Every bite is rich, extra chocolate-y, and so good.

Ingredients

Cake

  • ⅓ cup natural process cocoa powder
  • 1 teaspoon espresso powder
  • 6 Tablespoons boiling water
  • ¾ cup all purpose flour*
  • ⅔ cup granulated sugar
  • 1 teaspoon baking powder
  • ¼ teaspoon baking soda
  • ⅓ teaspoon salt
  • 1 large egg room temperature
  • 6 Tablespoons whole milk
  • 3 Tablespoons vegetable oil
  • ¾ teaspoon vanilla extract

Mousse

  • 2 cups heavy cream cold
  • 1⅓ cups dark chocolate pieces
  • 1½ teaspoons powdered gelatin
  • 2 Tablespoons water
  • 2 large eggs
  • 2 large egg yolks
  • 3 Tablespoons granulated sugar

Mirror Glaze

  • 1½ teaspoons powdered gelatin
  • 2½ Tablespoons water
  • 6 Tablespoons granulated sugar
  • ¼ cup water
  • 1 Tablespoon corn syrup
  • ⅓ cup natural process cocoa powder
  • ¼ cup heavy cream
US Customary - Metric

Instructions

Cake

  • Heat oven to 350℉.
  • Spray an 8 inch round pan with baking spray.
  • In a small bowl, combine cocoa, espresso powder, and water.
  • Whisk until smooth. Set aside.
  • In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt.
  • Add egg, milk, oil, and vanilla.
  • Mix well.
  • Add chocolate mixture.
  • Mix only to blend.
  • Pour into prepared pan.
  • Bake for 25 minutes, or until done.

Mousse

  • Whip cream to stiff peaks.
  • Refrigerate until needed.
  • In a small bowl, dissolve gelatin in water. Set aside.
  • In a medium bowl, whisk together eggs, egg yolks, and sugar.
  • Set bowl over a pot of simmering water.
  • Cook, whisking constantly, until mixture reaches 135℉.
  • Remove bowl from heat.
  • Stir in gelatin.
  • Beat with an electric mixer until mixture is light and fluffy, about 3-4 minutes.
  • Place chocolate in a medium-sized microwave safe bowl.
  • Heat on high in 15 second increments, stirring well after each, until chocolate is melted and smooth.
  • Stir into egg mixture.
  • Fold whipped cream into chocolate mixture, ⅓ at a time.

Putting It Together

  • Turn cooled cake out of pan.
  • Trim to level.
  • Line 8 inch round pan with plastic wrap.
  • Place cake layer in pan.
  • Top with mousse.
  • Cover and refrigerate overnight or until set.
  • Smooth sides of mousse with an offset spatula before glazing.

Mirror Glaze

  • In a small bowl, dissolve gelatin in 2½ Tablespoons water. Set aside.
  • In a small saucepan, combine sugar and ¼ cup water.
  • Heat and stir over medium heat until sugar is dissolved.
  • Remove from heat.
  • Stir in corn syrup and cocoa powder.
  • Mix in cream.
  • Return to heat.
  • Cook and stir over medium heat until mixture reaches 190℉.
  • Remove from heat.
  • Allow to cool to between 130℉ and 140℉.
  • Stir in gelatin.
  • Continue stirring until melted and smooth.
  • Strain into a glass bowl.
  • Use a rubber spatula to stir gently until all the streaks are gone.
  • Allow to cool to 80℉.
  • Immediately pour over cake.

Notes

*This recipe was written using an average of the dip and sweep method for measuring flour and the spoon and level method. If you are using a scale, you will need to add 3/4 oz or 22 g  to the measurement for each cup of flour.
  • You can boil the water in a microwave, on the stove top, or in a kettle!
  • Mixing the boiling water, cocoa powder, and espresso powder is a technique called, “blooming”. This allows for the powder to dissolve and release all of it’s amazing flavors. That means you wind up with a much more flavorful and delicious cake!
  • Be sure to check the expiration dates on your baking powder and baking soda.
  • Use a cake tester or a toothpick to test when this cake is done.
  • When making the chocolate mousse, be sure that the gelatin is entirely dissolved into the egg mixture before moving forward. You don’t want chunks of gelatin in your mousse!
  • The melted chocolate NEEDS to be warm for this recipe. If it gets cold by the time you add it to the egg mixture, you will have chunks of chocolate in your mousse.
  • Be careful to not over whip your cream!
  • When folding in the whipped cream, do not over fold. You don’t want to deflate the mousse.
  • Do NOT boil the mirror glaze or over-mix it! Be as gentle with it as you can.
  • Once the mirror glaze is poured onto the cake, this is the time to move it! Place it on any cake plate or serving platter you wish to have it on to serve.
  • Try and keep the mirror glaze as thin as possible! It's not the most pleasant thing to bite into if there's a large quantity.
  • You can use an offset spatula to help move/thin the mirror glaze once it's on the cake.
  • If there are bubbles in your mirror glaze, no worries! Once the glaze is set, use a heated offset spatula to smoothen out any imperfections.

Nutrition

Serving: 1sliceCalories: 672kcalCarbohydrates: 65gProtein: 12gFat: 43gSaturated Fat: 27gPolyunsaturated Fat: 5gMonounsaturated Fat: 9gTrans Fat: 0.04gCholesterol: 193mgSodium: 275mgPotassium: 428mgFiber: 4gSugar: 45gVitamin A: 1168IUVitamin C: 1mgCalcium: 208mgIron: 3mg

Nutritional information is only an estimate. The accuracy of the nutritional information for any recipe on this site is not guaranteed.