Why It Works
- We love using our microwave. In addition to baking the cakes in the microwave, we use it to dry out and "roast" them. This technique intensifies their natural flavor and gives them a light crisp texture.
- We mix the batter in a food processor, adding a splash of bourbon for added flavor, and then process in the nuts and marshmallow. The marshmallows provide extra leavening for the cakes.
- We portion the cake batter into paper cups that have been vented to allow steam to escape.
Microwave cakes have now become mainstream. Sort of. They were invented by Albert Adria. He used a whipped cream dispenser and a microwave to make almost instant light-as-air cakes. The technique has been adapted and adopted by chefs and home cooks around the world. It's a favorite of ours and we have formulated a number of recipes, from Danish to cornbread.
The problem? Each time we published a new recipe, a reader would complain about the use of the whipped cream canister. While many gear-heads and serious home cooks have one, they're just not as common as the food media would like us to believe. They also have their limitations: You can't make a microwave sponge cake with any sort of chunky inclusions when using the canister.
We decided that there had to be a way to make these cakes without using the gadget.
We thought about soufflé cakes, how they have a similar light and airy texture, but are softer and less stable than microwave sponge cakes. Soufflé cakes are lightened with whipped egg whites. So we set about making a microwave cake using a hybrid meringue as our leavening. Alex had a craving for Rocky Road so we decided to use that as the flavor base giving us the extra challenge of how to add inclusions like marshmallow, toasted nuts, and chocolate to the cake while changing the base recipe.
To make our cakes, we start by toasting walnuts in the microwave. It's a really easy method and results in more even toasting than on the stovetop and is faster than toasting in the oven.
Next, we melt a combination of dark and white chocolate by running it in the food processor, letting the heat of friction do the work for us. A little bit of peanut oil adds some tenderness to the cakes and brown sugar lends flavor as well as some moisture-retention properties.
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Next we add flour, cocoa powder, salt, and powdered egg whites to the base and blend it up again. Finally, 3 egg yolks, milk, and a splash of bourbon get blended in until a fully smooth batter is formed.
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After making this rich batter, our plan was to fold it into a whipped egg white mixture for leavening.
In the process of testing this we discovered something really interesting. Our first round of cakes was seriously dense, until we folded in miniature marshmallows. When we microwaved the cakes with the marshmallows, they expanded and pushed the rising cake batter up and out of the cups. They provided steam leavening and created huge holes in the finished cake. Not ideal results, but really interesting and worth exploring.
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We adapted this idea and instead of using whole marshmallows and nuts, we decided to pulse some into the batter to chop them up a little more finely. The inclusions add gooey texture, sweet flavors, and additional leavening. Turns out that the miniature marshmallows are the macro-leaveners in our micro cakes.
The rest is pretty straightforward. We whip a few egg whites in a stand mixer until frothy, then we add some powdered sugar and keep whipping until stiff glossy peaks form.
To this we add our chocolate base...
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...and start very gently folding it in.
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The key here is to combine the two elements without deflating the whipped whites—the inclusion of plenty of air is what keeps these cakes light and tender.
The very best part about these little cakes? They don't require any special baking equipment beyond little paper cups. To bake them, just poke a hole in the bottom of a paper cup along with three small holes around the perimeter for venting.
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Pour the batter into the cup, and microwave them for just 45 seconds. They come out light as air, puffy, and moist, and while they're great eaten hot out of the microwave, we actually think they have the best flavor when eaten at room temperature.
October 2014
Recipe Details
Microwave Rocky Road Sponge Cakes Recipe
Prep20 mins
Cook25 mins
Active20 mins
Total45 mins
Makes20 small cakes
Ingredients
- 100g walnut halves
- 150g 60% dark chocolate chips
- 150g white chocolate chips
- 50g dark brown sugar
- 50g peanut oil or walnut oil
- 50g all-purpose flour
- 50g cocoa powder
- 18g powdered egg whites
- 3g salt
- 3 large eggs, separated
- 175g whole milk
- 30g Knob Creek Bourbon, or your favorite
- 100g powdered sugar
- 100g miniature marshmallows
Directions
Put the walnuts in an even layer on a microwave-safe plate. Microwave the walnuts for 1 minute. Stir the walnuts on the plate and microwave for 1 minute longer. Stir the walnuts again and continue to microwave the walnuts in 1-minute intervals for a total of 5 minutes. Let the walnuts cool on the plate.
Put the dark chocolate, white chocolate, brown sugar, and peanut oil into a food processor. Process until the chocolate melts and the mixture is smooth, about 3 minutes.
Add the flour, cocoa powder, powdered egg whites, and salt into the food processor and pulse the mixture 10 times to blend the ingredients, about 12 seconds total.
Add the 3 egg yolks, milk, and bourbon to the food processor and process until it forms a smooth batter, about 1 minute. Stop and scrape down the sides once during this process.
Add the walnuts and miniature marshmallows into the food processor and pulse 10 times, about 12 seconds, until they are minced and mixed into the batter.
Whip the 3 large egg whites on medium in a stand mixer with the whisk for 2 minutes, until they begin to get frothy. Remove the bowl from the mixer and sift the powdered sugar over the egg whites. Return to the stand mixer and whip the mixture on medium speed until it forms stiff, glossy peaks, about 5 minutes. Remove the bowl from the mixer and knock any egg white that clings to the whisk back into the bowl.
Use a rubber spatula to scrape the chocolate batter into the bowl of whipped egg whites and then fold them together to form a light, uniform batter. This takes about 30 seconds.
Use a pairing knife to poke a hole in the bottom of each paper cup and 3 holes evenly around the circumference of the cup. Reserve the cups. Don’t worry; the batter will not seep out through the holes. Put 2 ounces (4 tablespoons) of batter into each cup. We use an ice-cream scoop to do this. Microwave 1 cake at a time for 45 seconds on high power. Remove the cake from the microwave and immediately invert it onto a heatproof tray. Continue to microwave the remaining cakes until they are all cooked. The cakes can be eaten warm, room temperature, or refrigerated. We think they have the best flavor at room temperature. They will stay fresh for up to 3 days refrigerated inverted.
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Special Equipment
Microwave, food processor, stand mixer with whisk attachment, 10-ounce paper cups
Make-Ahead and Storage
The cakes can be stored upside-down in their cups on a plate or tray in the refrigerator for up to 3 days.
Read More
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- Microwave Mocha Mug Cake
- Chocolate Soufflé
- Baked Chocolate Mousse Cake
- Microwave Shortcuts Every Home Cook Should Know
