Peanut Butter Chocolate Mousse Cake

One of my cool aunts asked me to make a birthday cake for her daughter. When I asked her what kind of cake she was thinking about, she sent me a picture of a Reese’s cake decorated with the peanut butter cups themselves. I took the challenge under one condition: the family must act as my guinea pigs and provide me with constructive criticism. There was another tiny condition: that they would leave me a small piece of cake to try, but somehow all the evidence disappeared after the knife started cutting the cake.

Reese’s peanut butter cups are tasty but a little too dense and sweet for my taste. Despite its popularity, I prefer Reese’s Pieces. They’re peanut butter lentils covered by a thin chocolate coating. Just like M&M’s, but so much yummier (did I mention they’re filled with peanut butter already?).

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My family gets excited about peanut butter as much as I do. I tried to make a cake that is not too dense. A mousse cake in three layers: a brownie base with peanut chunks, a dark chocolate mousse in the middle, from my favorite mousse cake recipe, and a light peanut butter mousse on the top. I glazed the cake with dark chocolate ganache to offset the peanut butter sweetness just in case. Although I didn’t get to taste the final product, I have to admit that I didn’t stop licking my fingers while making this cake.

And this is the judges’ verdict: According to my aunt, the family reallyyyyyy liked the cake (yup, that’s really with 6 ‘y’s).  The peanut butter mousse layer was heavenly. In her words, the peanut butter flavor was exactly right. I had my own hesitations about the base layer. She did agree with me that the base was a little hard. The rest of the family loved it anyway. That always happens with brownie bases. They have a tendency to get a bit hard while the mousse sets in the freezer. Oh well, I will try another version of the cake with a different base soon enough and update this post.

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Ingredients

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Peanut brownies
70 g dark chocolate
90 g butter
180 g sugar
110 g eggs (2L)
140 g flour
A pinch of salt
80 g chopped peanuts

Gelatin mass
10 g gelatin powder
50 g water

Dark chocolate mousse
80 g egg yolk
35 g eggs
40 g water
60 g sugar
20 g gelatin mass
320 g dark chocolate
270 g heavy cream

Peanut butter mousse
80 g egg yolk
35 g eggs
40 g water
60 g sugar
35 g gelatin mass
145 g white chocolate
145 g peanut butter
25 g dark chocolate
270 g heavy cream

Chocolate ganache
150 g dark chocolate
150 g heavy cream

Decoration
Chopped peanuts

Equipment
A round ring, 22 cm diameter and 6-8 cm height
Acetate strip, 10 cm height
2 double boilers
Thermometer

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Advance prep

Gelatin mass:  Sprinkle gelatin powder over the water, mix well and keep in the fridge for at least half an hour. Cut into small pieces before use.

Peanut brownies

Place a layer of aluminum foil on a baking tray, followed by a layer of parchment paper and set the ring on top. Fold the edges of the paper and foil to the sides of the ring and tighten them so that the batter won’t spill out of the bottom of the ring. Lightly grease the inner wall of the ring and line it with parchment paper. Set aside.

Preheat the oven to 180 °C (350 °F).

Melt the chocolate with the butter on a double boiler, while mixing all along. Remove from heat and let it cool for a little bit. Add sugar and mix well. Beat the eggs into the mixture. Add flour and salt and fold just until uniform. Add the chopped peanuts and fold them into the mixture as well.

Pour the batter into the ring and flatten the surface with a spreading spatula. Place the tray in the oven and bake for about 25 minutes. Stick a toothpick in the center of the brownies to check if it’s ready. The toothpick should come out almost dry. Let the brownies cool at room temperature.

Release the ring and remove the parchment paper. Place the brownies on a serving plate. Wash the ring, dry it and place it around the brownies, with an acetate sheet in between.

Dark chocolate mousse

Whip the heavy cream until you almost get soft peaks (beware not to over whip, the goal is to get a texture that resembles thick yogurt). Keep in the fridge.

Melt dark chocolate on a double-boiler. Once the chocolate has melted, turn off the flame and leave the bowl on the double-boiler to keep the mixture warm.

Put egg yolk, eggs, sugar and water in a stainless steel bowl and whisk until uniform. Place the bowl on a second double-boiler and heat gently (low-medium fire) to 80-82 ° C (176-180 ° F), while mixing all along. Once the desired temperature is reached, strain the mixture immediately into the mixer bowl and whip on high speed for about 5 minutes, until the egg mixture cools. When you drop a spoonful of the mixture into the bowl it should fall back in ribbons and disappear into the mixture slowly.

In the meantime, melt the gelatin mass on a double-boiler and remove the melted chocolate from the hot steam. Make sure the chocolate temperature is between 45-50 ° C (113-122 ° F). If the temperature is too high, I recommend transferring the chocolate into another bowl to cool it faster.

Add the melted gelatin mass to the egg mixture and mix a little. Add the warm chocolate and mix until uniform. The texture will become viscous. Remove the heavy cream from the fridge and whip it a little more (remember, yogurt texture).

Fold the heavy cream into the egg mixture in three parts. Pour immediately into the ring over the brownies. Give it a little shake to flatten the mousse and keep it in the freezer for about an hour or two.

Peanut butter mousse

Whip the heavy cream until you almost get soft peaks (beware not to over whip) Keep in the fridge.

Melt white chocolate and dark chocolate on a double-boiler. Once the chocolate has melted, turn off the flame, add peanut butter and mix until uniform. Leave the bowl on the double-boiler to keep the mixture warm.

Put egg yolk, eggs, sugar and water in a stainless steel bowl and whisk until uniform. Place the bowl on a second double-boiler and heat gently (low-medium fire) to 80-82 ° C (176-180 ° F), while mixing all along. Once the desired temperature is reached, strain the mixture immediately into the mixer bowl and whip on high speed for about 5 minutes, until the egg mixture cools. When you drop a spoonful of the mixture into the bowl it should fall back in ribbons and disappear into the mixture slowly.

In the meantime, melt the gelatin mass on a double-boiler and remove the melted chocolate mixture from the hot steam. Make sure the chocolate temperature is between 45-50 ° C (113-122 ° F).

Add the melted gelatin mass to the egg mixture and mix a little. Add the warm chocolate mixture and mix until uniform. The texture will become viscous. Remove the heavy cream from the fridge and whip it a little more.

Fold the heavy cream into the egg mixture in three parts. Pour immediately into the ring over the dark chocolate mousse. Give it a little shake to flatten the mousse and keep it in the freezer for at least two hours (and even more – It’s easier to remove the acetate strip without affecting the form of the cake when it’s frozen solid).

Chocolate ganache

Break the chocolate into small pieces and put them in a measuring pitcher. Bring heavy cream to a boil. Pour immediately over chocolate, making sure all the chocolate is covered.

Mix a little bit with a spatula and then use a hand blender to blend it to a uniform consistency. Let the ganache cool a little at room temperature.

Putting it all together!

After the mousse has set in the freezer, release the ring and peel off the acetate strip. Pour the ganache over the top of cake right at the center. Lift the cake and tilt it to the sides just a bit to let the ganache drip from the sides.

Decorate the top of the cake with chopped peanuts. Keep in the fridge. Let the cake defrost in the fridge before serving (at least 3-4 hours).

Yum