The right opportunity to confect this cake version of a Mojito presented itself just after my birthday, a couple of weeks ago. With birthday celebration plans for Jeff, Dad, and myself right around the corner, it was time to try something new. The minute I saw this recipe in Warren Brown's Cake Love cookbook a couple of years ago, I wanted to make it! Mint and lime are anything but common cake flavors, so I knew I was gambling on a cake that may not be as crowd-pleasing as the predictable chocolate or vanilla standard, as well as committing myself to a day-long cake creating adventure. This is the most complex and time consuming cake I've made. And I've made a lot of cakes.
Warren Brown's recipes are so well-written that its REALLY hard to screw anything up. His instructions are thorough and his measurements are easy to understand, but most do require a standing mixer and a passion for baking that makes the undertaking of a recipe like the Mojito Pound Cake enjoyable.
From the time I began oven-drying the mint to the time the cakes came out of the oven, it took me 2 1/2 hours of active prep and baking time. This is due to the drying of the mint, the zesting of the limes, the segmenting of the limes, and accurately measuring all the different ingredients. Of these 2 hours, I've excluded the additional time required to go out to the store to buy more mint, since after I dried my first batch (the recipe calls for just 1/3 cup of oven dried mint but doesn't specify the quantity of fresh mint required to yield it), there were barely two tablespoons!
Upon tasting the cake out of the oven, the lime flavor wasn't as strong as I'd hoped, but the mint DOMINATED! Since I couldn't taste much of the lime (and I'm a lime-lover), this perfectionist set forth to incorporate more lime flavor into the final product.
After an hour of flipping through cookbooks looking for ideas and cursing under my breath, I decided to make a lime curd to take up one of the layers in between the cake, along with a lime syrup to soak each cake layer.
The results were what I had hoped for: bright lime flavors with mint undertones brought together by a creamy rum Italian Buttercream frosting. If you're going to make this cake, you've got to make the buttercream! Its worth the extra effort, its delicious, and it brings all the flavors together.
The original recipe also calls for lime segments to be added to the cake batter. These bits of lime made for some pretty bitter bites, so moving forward I would substitute a couple tablespoons of lime juice for the whole lime pieces.
Below is my take on Warren Brown's Mojito Pound Cake with Rum-Flavored Italian Meringue Buttercream originally published in CakeLove: How to Bake Cakes from Scratch by Warren Brown, and the recipes for the frosting, the lime curd, and the lime syrup.
3 whole cloves (ground into a fine powder)
5 ounces of fresh mint, to yield 1/3 cup oven dried mint (crumbled)
2 1/4 cups + 2 tablespoons unbleached all-purpose flour
1/4 cup potato starch
1 teaspoon salt
1/4 teaspoon baking soda
2/3 cup sour cream
1/4 cup half-and-half
3 tablespoons dark rum
2 teaspoons vanilla extract
1 teaspoon molasses
1 teaspoons lemon juice
2 tablespoons lime juice
2 sticks room temperature unsalted butter
2 1/4 cups extra-fine granulated sugar
2 teaspoons lime zest
4 large eggs
2 large egg yolks
Preheat the oven to 350 degrees.
For the Cloves: pulverize into a powder using a mortar and pestle or coffee grinder.
For the Mint: Break leaves from stems, and place the mint leaves in the center of a sheet of aluminum foil. With the mint in the center of the foil, pull up the side of the foil as if to make a pouch. Next step is important if you don't want pieces of foil blended with your dried mint! Poke 3 sets of holes thru the sides of the foil to the OUTSIDE of the pocket. Each side of the pocket should now have ventilation holes. Bring the edges together to form a pouch, and close the top loosely so steam can escape. Place in oven. Check on the mint every 10 minutes until its dry and crisp, and each leave easily crumbles when rubbed between thumb and forefinger with no wet part of leaf remaining behind. Discard stems if you missed any.
Incorporate oven-dried mint, cloves, and the rest of the of the dry ingredients into a bowl, whisk briefly, and set aside. Incorporate all of the liquid ingredients into a bowl, whisk briefly, and set aside. Measure the butter, sugar, eggs, and yolks into separate bowls and set aside.
In the bowl of a standing mixer (fitted with the paddle attachment) cream together the butter, sugar, and lime zest on the lowest setting for 4 to 5 minutes.
With the mixer still on the lowest speed, add the eggs one at a time followed by the yolks, fully incorporating after each addition.
Add the dry ingredient mixture, alternating with the liquid mixture in 3 to 5 additions each, beginning and ending with the dry mixture. Move swiftly through this step to avoid overworking the batter. Don’t wait for the dry or liquid mixtures to be fully incorporated before adding the next. This step should take a total of about 60 seconds.
Stop the mixer and scrape down the sides of the bowl. Mix on medium speed for 15 to 20 seconds to develop the batters structure.
Prepare the cake pans. For 9-inch-round cakes, line the bottom of each pan with parchment. Deposit the batter evenly into the pans and smooth out with an offset spatula, making sure the pans are two-thirds full. Bake for approximately 30 to 35 minutes, until the tops are golden brown, a toothpick comes out with a few wet crumbs, and the center doesn't jiggle when pan is moved.
Remove the pans from the oven and cool to room temperature on a wire rack, about 25 to 30 minutes before removing from the pan. Loosen the cake gently from the pan with a small offset spatula and invert onto a flat surface. Remove the parchment from the bottom of each cake and wrap the layers tightly in plastic. You can refrigerate the layers overnight or up to 5 days before frosting. Note: I’ve left the layers in the fridge for about 3 hours, and this worked fine for me! Next, make the lime curd.
Lime Curd (can be made up to 2 days ahead of time and kept in an airtight container in the fridge)
2 tsp finely grated lime zest
4 large egg yolks
1/2 cup sugar
6 tbsp lime juice, freshly squeezed and strained (about 3 medium limes)
Have a strainer ready and suspended over a medium bowl that holds the lime zest. In a heavy nonreactive saucepan, beat the yolks and sugar with a whisk until well-blended. Stir in the lime juice, butter, and salt. Cook over medium-low heat, stirring constantly (be sure to scraped the sides of the pan), until the mixture is thickened and resembles hollandaise sauce; it should thickly coat a wooden spoon; it must not be allowed to boil or it will curdle. Whenever steam appears, remove the pan briefly from the heat, stirring constantly to keep the mixture from boiling. When the mixture has thickened (196F on an accurate thermometer), pour it at once into the strainer (or directly into the bowl with the zest if not straining). Press with the back of a spoon until only the coarse residue remains. Gently stir in the zest into the curd and allow it to cool to room temperature.
Lime Syrup (can be made up to 2 days ahead of time and kept in the fridge)
Extra-fine granulated sugar, 16 ounces (2 cups)
Water, 1¼ cups
2 Tablespoons Lime Zest, finely grated.
Combine the sugar and water in a 2-quart, heavy-bottomed saucepan and stir thoroughly. Bring the mixture to a light simmer over medium-high heat to dissolve the sugar. Do not bring to a rolling boil. Immediately remove the mixture from the heat and set aside to cool completely.
Rum-Flavored Italian Meringue Buttercream (make the day of assembly)
5 egg whites
1 1/4 cups extra-fine granulated sugar
1/4 cup cold water
1 pound (4 sticks) unsalted butter
2 to 4 tablespoons of dark rum (to taste)
Set out the ingredients and the equipment.
Separate the egg whites into the bowl of a standing mixer fitted with the wire whip attachment. Measure 1 cup sugar and the water into a 1-quart, heavy-bottomed saucepan. Gently stir with the candy thermometer to combine. Place the remaining 1/4 cup sugar into a small bowl and set aside. Cut the butter into tablespoon sized pieces and set aside in a medium bowl.
To make the sugar syrup, place the candy thermometer in the saucepan and heat the mixture over medium-high heat. Partially cover with a lid to capture the evaporating water-this helps to moisten the sides of the saucepan to prevent sugar crystals from forming.
With the mixer on high speed, begin whipping the egg whites to stiff peaks. When the peaks are stiff you have a meringue. Keep the mixer running and pour the 1/4 cup of sugar into the meringue.
Raise the heat under the sugar syrup to bring the syrup to 245 degrees, if it is not there already. When the syrup is at 245 degrees, remove the thermometer and slowly pour the syrup into the meringue.
After 1 or 2 minutes reduce the mixer speed to medium for 3 or 4 minutes, or until the meringue is cooled. Add the butter 1 tablespoon at a time. Increase the mixer speed to high for 1 to 2 minutes, or until the butter is fully incorporated. Finally add in the dark rum and incorporate!
To Assemble Cake:
Divide cakes into layers: Carefully trim very outer golden edges of each cake using a bread knife. I do this so the buttercream more easily adheres to the cake. Divide each cake into 2 layers using a cake knife, or very carefully using a bread knife. Set aside.
Apply syrup to the layers: Using a pastry brush (I prefer silicone), gently dab the syrup onto the cake leaving no part untouched. You'll probably have about a 1/2 to 3/4 of syrup leftover. Store in the refridgerator.
Assemble the layers: Place one layer on bottom. Apply about 1/4 inch of buttercream to within 1/2 inch of the edge of the cake. Place another layer on top. Apply all the lime curd to within 1/2 inch of the edge. Carefully apply enough buttercream on top of the curd so that this layer is as evenly spaced as the last. Add another cake layer and apply another 1/4 inch of butter cream. Add final layer of cake, and apply a thin coat to top, and finally to sides. This is called the "crumb coat", so you'll see some crumbs in the frosting. Refrigerate for 30 minutes or until this first coating has solidified. Remove from fridge and apply more buttercream. This layering should appear flawless. If crumbs still appear, put cake in fridge and apply more frosting after last layer has solidified. An additional batch of buttercream might be required, so use frosting wisely! Garnish with Turbinado Sugar and a few fresh mint leaves.