This Blackberry mousse cake has everything it needs to be a great dessert. The base is a chocolate Italian sponge cake. It’s dark and moist, sweet, and has the distinctive ﬂavor of chocolate. The delicate white chocolate mousse is light, and soft in both sweetness and ﬂavor. However, the mousse suspends a blackberry purée that’s been set with a touch of gelatin. This fruit layer is intense in both its color and its tart ﬂavor. The ﬁnal touch is a glaze of melted white chocolate colored purple on top of the cake; it provides a startling white chocolate ﬂavor, and vibrant blackberry purple color that stands out in contrast to the white chocolate mousse. **REMEMBER THE MIRROR GLAZE WILL ONLY WORK ON A MOUSSE CAKE *** An airy texture is key to the mousse’s role in the dessert, so be careful when whipping the heavy cream. When using an electric mixer, there’s very little time difference between whipped cream that’s just shy of stiff peaks and cream that’s on the verge of becoming butter. The mousse with the white chocolate is light and creamy and so yummy! The blackberry puree inside the mousse is just the right amount of tanginess. I wish I had put the blackberry puree higher in the cake, because it blends in with the chocolate sponge cake at the bottom. I think next time I would also make a thicker layer of blackberry. *To make the blackberry purée “ﬂoat,” begin by spooning half of the white chocolate mousse over the cake layer in the spring form pan. Set the circle of blackberry purée in the pan’s center and push it into the mousse until the purée is at the middle of the pan. The mousse will rise around the purée and up the pan’s sides. *To complete the illusion of the ﬂoating blackberry, add the remaining mousse to the spring form pan; it will exceed the top of the pan. Then use the pan’s edges to guide a large metal spatula across the top of the cake to smooth it.
- 120 grams (1/2 cup+1½ tablespoon) granulated sugar
- 4 extra large eggs, at room temperature
- 100 grams (1 cup minus 1 tablespoon) cake flour, sifted (if you use all-purpose flour 100 grams = 1 cup minus 2 tablespoons)
- 20 grams (3 tablespoons) unsweetened cocoa powder
- YOU WILL HAVE A LOT OF BATTER LEFT OVER
- 12-oz. package frozen blackberries
- 2 tsp. un flavored powdered gelatin
- 1/4 cup sugar
- 8 oz. good-quality white chocolate, chopped fine
- 1/4 cup water
- 1 envelope unflavored powdered gelatin
- 2 1/2 cups heavy cream
- Take the eggs out from the fridge ahead of time or soak them for a few minutes in a bowl of warm water.
- Preheat the oven to 170 degrees C (338 degrees F).
- Butter and flour (or spray with baking spray) a 20 cm (8 inch) pan.
- Put the eggs and sugar in the bowl of your stand mixer.
- Beat the eggs until very fluffy and pale yellow (about 15 minutes on medium/high speed). To test that it has been beaten enough, let some of the mixture fall into the bowl, if it remains "sitting" on top it means that it's ready.
- Sift the flour and cocoa powder on top of the egg mixture, a little at a time, and fold it gently with a wooden spoon, from bottom to top.
- Pour the batter into the prepared pan. Don't smooth the top or bang the pan on the counter, leave it as it is!
- Bake for 40 minutes or until a toothpick inserted into the center comes out clean. (Don't open the oven for the first 20 minutes!)
- Turn off the oven but leave the chocolate Italian sponge cake inside (put a wooden spoon to keep the oven door slightly open) for at least 10 minutes so it can cool down slowly. After that, remove it from the oven, let it cool 10 more minutes, loosen around the edges with a knife, then flip the cake on a wire rack upside down (without the pan) to cool completely.
- This part of the recipe calls for an 8-in. cake pan because that’s the round pan most people have. However, since you’ll only need a 51/2-in. circle of purée, you won’t use all the purée. Use a smaller round pan if you have one; just fill it to a depth of 3/4 in.
- Line an 8-in. cake pan with plastic wrap, leaving about 4in. of excess plastic hanging over the pan’s sides.
- Defrost the berries until soft. Purée them in a food processor for about 30seconds, or until smooth. Set a fine sieve over a small, nonreactive saucepan.
- Pour a small amount of the blackberry sauce in the sieve and force it through with a spatula. Repeat the process until you have strained all the blackberry purée.
- Sprinkle the gelatin over the purée.
- Allow the gelatin to soak and soften, about 5min., and then stir.
- Heat the purée over medium heat and continue stirring until the gelatin melts completely.
- Add the sugar and stir until dissolved.
- Cool the blackberry mixture slightly and pour it into the plastic-lined cake pan.
- Freeze for an hour or until just set, and then drape the excess plastic over the top of the purée. Continue freezing for at least 12 hours. If you won’t be using the purée within 24hours, prevent freezer burn by popping it out of the pan and completely wrapping it in plastic or putting it in a plastic bag.
- Put the chocolate in a metal bowl (1 qt. or larger) that will fit snugly over a saucepan. (You also can use a double boiler.)
- Fill the saucepan with 1 in. of water and heat it until it’s on the verge of simmering.
- Remove the pan from the heat and set the bowl of chocolate on top of the saucepan.
- Stir the chocolate with a rubber spatula to encourage melting; however, don’t be concerned if the chocolate doesn’t melt entirely.
- Pour 1/4 cup water in another saucepan and sprinkle in the gelatin.
- Let the gelatin soak for 5 min., and then set the saucepan over medium heat and stir until the gelatin dissolves.
- Pour 1/2 cup of the cream in another small saucepan and bring it to a boil.
- Remove the saucepan from the heat immediately.
- Add the gelatin to the hot cream and stir until well mixed.
- Add this mixture to the melted chocolate and stir well with a spatula until the mixture is very smooth.
- Remove the bowl from the pan and allow the chocolate mixture to cool until it’s just warm.
- Use an electric mixer to whip 2 cups cream until it just holds stiff peaks.
- Use a rubber spatula to gently fold half of the whipped cream into the slightly warm chocolate mixture.
- Add the remaining whipped cream and fold gently until smooth.
- Don’t over fold the mixture; it should still have a few distinct streaks of white chocolate and whipped cream.
Remove the blackberry purée from the freezer and unwrap it. Use a 51⁄2-inch ﬂan ring to cut a smaller circle from the purée. (You also can use a small plate as a template, or merely “eyeball” it, and cut a circle with the tip of a sharp knife.) Lay the purée circle in the center of the springform pan and push it into the mousse until it “ﬂoats” approximately in the middle of the pan. The mousse should begin to rise around the purée and up the pan’s sides. Add the remaining mousse; it should slightly exceed the top of the pan. Using the pan’s edges as a guide, scrape a large metal spatula across the top to remove the excess and to smooth the top of the mousse.
Put the cake, uncovered, in the refrigerator for about an hour to let the mousse set, and then cover the top with plastic wrap. The cake must be refrigerated for at least 8 hours before glazing. At this point, you can also freeze the cake for up to a week. (If you do freeze it, you must defrost it in the refrigerator overnight before you glaze it.)
Remove the cake, still in the pan, from the refrigerator. Take the cake out of the pan and place on top of a cup or bowl. If you need to, loosen the pan by heating it gently with a hair dryer on medium heat, directing the hot air around the sides of the springform pan. Use a back-and-forth motion and be careful not to overheat. It should take no more than 10 to 15 seconds for the pan to sufﬁciently loosen. Carefully slide the long, narrow spatula between the cake and the pan’s sides to make sure the cake is ready to be removed from the pan.
Unsnap the springform pan, remove the cake, and put it on a cup, bowl, or can. Make sure you have something under the cake to catch the excess glaze like a cookie sheet. Pour the glaze on top. Rotate the cake so that the glaze covers the entire surface. If any bubbles appear on the glaze’s surface, quickly and gently pierce them with the tip of a small, sharp knife. To cut the cake, heat a thin, sharp knife with a hair dryer or the ﬂame of a gas stove. Slice the cake gently using single downward motions, one piece at a time, and arrange the slices on individual plates. If you like, decorate with fresh blackberries. CAKE COUNTDOWN This cake can be made in steps in advance so it isn’t as much work on the final day. Follow this guideline if you like. Chocolate cake—one week to one day before assembly. If you make the cake more than two days in advance, remove the cake from the pan and wrap it in plastic to keep it moist. White chocolate mousse— immediately before assembly. When you make the mousse, the cake and purée should already be prepared. Assembly—one week to nine hours before serving. If you’re going to assemble the cake more than 48 hours before serving it, wrap the assembled cake and freeze it. Defrost it in the refrigerator overnight before you glaze it. Chocolate glaze—at least an hour before serving, but you must pour it on the cake immediately. The glazed cake may wait in the refrigerator for one day to an hour before serving, or you may wrap it and freeze it for a week. The cake should be frozen only once, however, so if you’ve frozen it during an earlier stage, don’t freeze it again.
This mirror glaze recipe is my own creation. I took many different recipes and translated them to English. I tried many times and came up with this recipe! I used grams because it is more precise. Just use a food scale to measure grams if you are used to using cups.
Mirror Glaze Recipe
20 g gelatin powder
120 g water
300 g light corn syrup
300 g sugar
150 g water
200 g sweetened condensed milk
300 g white chocolate good quality chopped fine
Bloom 20 g gelatin in 120 g water
boil 300 g corn syrup, 300 g sugar, and 150 g water
remove from heat and add gelatin
add condensed milk
pour over chocolate and mix until chocolate is melted completely (make sure you chop the chocolate really small before hand)
stir and make sure glaze reaches 95 degrees F
separate into multiple bowls if you want multiple colors
add food color
Let it cool for many hours until the glaze reaches 89.6 degrees F and is semi thick.
Pour glaze over cake
Recipe adapted from Fine Cooking
other Mousse cakes you might enjoy!