September Cupcake Hero Challenge

Quirky Cupcake has decided to hold a monthly Cupcake Hero Challenge. Here's how it works: "Each month a theme ingredient will be named. The theme ingredient will need to be used in either the cupcake, the frosting, the filling or all of the above if you choose." The theme ingredient for September is limes. As soon as I saw this, I knew I had to try to re-create keylime pie in cupcake format. Ok, so I didn't want to juice all those tiny key limes, so I used regular limes, but still think I did a pretty good job.



I used Magnolia's vanilla cupcake recipe, with a keylime mascarpone filling and a meringue icing. When you got all three components in one bite, it really did taste like keylime pie! I served these at a dinner party, and they were a huge hit! When I took them into the office, they disappeared quickly. One of my coworkers even went so far as to tell me it was the best cupcake she'd ever eaten. She later bought some from me for a surprise baby shower.



Key Lime Cupcakes
For Cupcakes:
1 1/2 cups self-rising flour
1 1/4 cups all-purpose flour
1 cup (2 sticks) unsalted butter, softened
2 cups sugar
4 large eggs, at room temperature
1 cup milk
1 teaspoon vanilla extract

1. Preheat oven to 350 degrees F. Line 2 (1/2 cup-12 capacity) muffin tins with cupcake papers.
2. In a small bowl, combine the flours. Set aside.
3. In a large bowl, on the medium speed of an electric mixer, cream the butter until smooth. Add the sugar gradually and beat until fluffy, about 3 minutes. Add the eggs, one at a time, beating well after each addition. Add the dry ingredients in 3 parts, alternating with the milk and vanilla. With each addition, beat until the ingredients are incorporated but do not over beat. Using a rubber spatula, scrape down the batter in the bowl to make sure the ingredients are well blended. Carefully spoon the batter into the cupcake liners, filling them about 3/4 full. Bake for 20 to 25 minutes, or until a cake tester inserted into the center of the cupcake comes out clean.
4. Cool the cupcakes in tins for 15 minutes. Remove from the tins and cool completely on a wire rack before filling and icing.

For Filling:
4 ounces cream cheese, softened
1/3 cup granulated sugar
2 teaspoons freshly grated lime zest
6 tablespoons fresh lime juice
1 cup mascarpone cheese (about 1/2 pound)
2 Tablespoons heavy whipping cream

In a bowl with an electric mixer beat cream cheese with sugar, zest, and lime juice until smooth. Beat in mascarpone. When mascarpone is fully incorporated, beat in cream, and allow to whip for another 30 seconds to a minute to lighten the filling.
Fill cooled cupcakes with your preferred filling method. I prefer to use a pastry bag to pipe the filling in through the bottom of the cupcake.

For Meringue Icing:
1/4 cup water
2/3 cup sugar
1/3 cup large egg whites -- (about 3)
1/8 teaspoon cream of tartar
2 tablespoons sugar
1 teaspoon vanilla

1. In a 3 cup saucepan, combine the water and 2/3 cup sugar. Place over low heat to dissolve the sugar, then increase the heat to medium high and boil, without stirring, until a candy thermometer reads 235 degrees. (Wash down any sugar crystals slinging to the sides of the pan with a brush dipped in cold water.)
2. Near the end of the boiling time, whip the egg whites with the cream of tartar until soft peaks form. Add the 2 tablespoons sugar, and continue to whip until the whites are stiff but not dry. With the mixer running, pour the syrup onto the whipped whites.
3. Continue to whip on medium speed, about 3 minutes more. Mixture will thicken, cool and form glossy, stiff peaks. Add the vanilla. Cool to room temperature, about 8-10 minutes, then frost cupcakes right away.

This recipe worked really well. It's a cupcake that manages to be both light and rich at the same time. The tanginess of the lime paired with the sweetness of the vanilla cupcake and meringue frosting are a match made in heaven!