Orange, White Chocolate & Kahlua Cupcakes

I made these for Mother's Day, and even my dad who generally doesn't like cake ate two. The recipe is a mix of a couple of different ones: the base cupcake is the "Orange Cupcakes" recipe from Cupcakes: A Collection of Delicious Recipes (with white chocolate added), and the frosting is from the "Kahlua and Orange Cupcakes" recipe from 500 Cupcakes.

• Ready In: 50 mins
• Serves: 16
• Yields: 16 cupcakes

Ingredients

• 1 3⁄4 cups flour
• 1  cup sugar
• 1⁄2 cup unsalted butter, softened
• 2  eggs (separated)
• 1  teaspoon vanilla
• 2 1⁄2 teaspoons baking powder
• 1⁄4 teaspoon salt
• 1⁄2 cup  orange juice
• 1⁄2 cup white chocolate chips
• 2  cups confectioners' sugar, sifted
• 1⁄2 cup unsalted butter, softened
• 1⁄4 cup mascarpone cheese (original recipe calls for sour cream)
• 2  tablespoons Kahlua
• 1  tablespoon  grated orange zest

Directions

1. Preheat oven to 350°F Line a cupcake baking tray with paper liners. Place the butter, egg yolks, sugar and vanilla in a large bowl and mix well until creamy.
2. In another bowl, add the baking powder, salt and flour and stir together. Slowly add the ingredients into the creamed egg yolk mixture, alternating with a little orange juice each time until all the ingredients are combined.
3. Beat the egg whites and fold carefully into the mixture, then fold the chocolate chips into the combined mixture. Spoon the mixture into the cupcake liners, up to about 2/3 full. Place in the oven and bake for around 15-20 minutes. Remove from the oven and leave to cool for 5-10 minutes. Transfer onto a cooling rack to cool completely.
4. For frosting, beat confectioners' sugar and butter in a small bowl until soft and creamy (because there's so little butter in comparison to the sugar, I found that I had to help it along a bit by getting my hands in the frosting). Beat in the mascarpone, Kahlua, and orange zest (for the zest, I didn't measure, I just zested 1 large orange into the frosting). Swirl onto cooled cupcakes.