Key Lime Cupcakes with White Chocolate Frosting
¾ cup (1 ½ sticks) unsalted butter, room temperature
1 cup granulated sugar
2 eggs, room temperature
1 teaspoon pure vanilla extract
1 rounded teaspoon fresh grated Key lime zest
1 ½ tablespoons fresh Key lime juice (bottled may be substituted)
1 ½ cups all-purpose flour
½ teaspoon baking powder
¼ teaspoon baking soda
¼ teaspoon kosher salt
½ cup buttermilk
1 1/3 cups loosely packed sweetened, flaked coconut
5 ounces good quality white chocolate chips (or chopped from a bar)
½ cup (1 stick) unsalted butter, room temperature
3 ½ cups powdered sugar, sifted
1/8 teaspoon salt
½ teaspoon pure vanilla extract
1 tablespoon fresh Key lime juice (may use bottled)
¼ cup sour cream
Green sanding sugar and lime jelly beans, for garnish
Preheat the oven to 325°F.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and sugar on high speed until light and fluffy (about 5 minutes). Turn to low speed, add the eggs one at a time, mixing well after each addition. Scrape the bowl down. Add the vanilla, zest and juice mixing well on low speed.
In a separate bowl, sift together the flour, baking powder, baking soda and salt. In 5 parts total, alternately add the dry ingredients and the buttermilk to the creamed butter/sugar mixture—beginning and ending with the flour mixture; mixing on low speed until incorporated. Remove the bowl from the mixer and scrape the bowl down. Fold the coconut into the cake batter.
Line a muffin pan with cupcake liners of your choice. Use a spring loaded ¼ cup ice cream scoop to fill each liner—this ensures uniformity (otherwise fill cups to slightly less than 2/3rds full). Bake for 25 minutes or until the tops just start to brown and the toothpick test comes out clean. Cool cupcakes in the pan for 10 minutes; transfer cupcakes to a rack to cool completely.
Meanwhile, make the frosting. In a small heat proof bowl seated on a pot of simmering water, slowly melt the white chocolate until smooth and chunk-free. Remove from heat and cool until lukewarm. In a bowl of a stand mixer fitted with the paddle attachment, beat the butter for a couple of minutes until light and fluffy. On low speed, gradually add the powdered sugar until well combined. Add the vanilla, lime juice, salt and sour cream; mix until very smooth. Add the melted chocolate and mix until incorporated.
Frost the cupcakes and garnish.
Notes: To help maximize the juicing process, roll the limes on a hard surface to help break up its flesh. Remember to zest the limes before cutting them for juicing. Fork tines stuck into the cut lime half, then twisted also helps to release the juice. Have a strainer ready the catch the seeds. In portioning the batter, draw your ¼ cup scoop up firmly against the side of the bowl to push out any excess measure. Swiping the sides of the scoop with a clean finger to clear it off helps to keep a neat “drop” into the cup. Start checking for doneness around the 21 minute mark.