While in London on a business trip a couple of weekends ago, I had a lemon cupcake with my afternoon tea and was thrilled to discover a surprise. Not only was this a delicious lemony cupcake with lemony buttercream, but it also had a lemon curd filling. It went beautifully with my extra-super-bergamot-flavored Earl Grey, and I promised myself I'd attempt to recreate them when I got back to my kitchen. So I did.
One of my friends, who has had many, many of my baked goods over the past few years, said these are the best cupcakes I've ever made. I think he's right, though I may top these with my birthday cupcakes next week....aren't you excited?
Make the lemon curd first, so you'll have it handy when you're ready to put some of it into the cake and into the icing. Instead of carving plugs out of the cupcakes and filling them, you can use a pastry bag to squeeze the curd into them. I think carving's more fun. You MUST use fresh squeezed-it-yourself lemon juice, the bottled concentrate stuff is horrible and will make horrible cupcakes.
Curd-Filled Lemon Cupcakes
For the Curd:
grated zest of two lemons
2/3 cup sugar
1/4 cup lemon juice
4 tbsp (1/2 stick) butter at room temperature
2 large eggs
pinch of salt
Bring about 1" of water to not-quite-simmering in a sauce pot. In a metal bowl, mix the lemon zest, sugar, and butter, blending with a hand mixer until creamy. Add the eggs one at a time. Mix in the lemon juice and salt, then place the bowl over the [almost] simmering water with the heat on low. Stir continuously with a wooden spoon until the curd has thickened enough to coat the back of the spoon, about ten minutes, then remove from heat.
Set aside 1/3 cup of curd to go in the icing, and 1/2 cup to go into the cake batter. The rest is for filling.
For the Cupcakes:
1 1/4 cup all-purpose flour
3/4 tsp baking powder
1/4 tsp baking soda
pinch of salt
1/2 cup butter at room temperature
1 cup sugar
1 tbsp lemon juice
2 tsp lemon zest
1 tsp vanilla
1/4 cup sour cream
3/4 cup buttermilk*
1/2 cup lemon curd
2 eggs at room temperature
*or, 3/4 cup milk with a tbsp of lemon juice in it, let it sit and curdle for 5 minutes or so before use.
Preheat oven to 350º.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt, set aside. In a large bowl, beat the butter with a hand mixer until smooth and fluffy. Add the sugar, beating until fluffy, then add lemon juice, zest, and vanilla. Mix in 1/3 of the flour, then half of the milk, then another 1/3 of flour, then the sour cream, then the rest of the milk, and then the last of the flour. Pour into paper-lined muffin tins, each one should be around 2/3 full.
Bake for about 25 minutes or until lightly browned around the edges, and let cool completely before filling and icing them.
For the Icing
1/2 cup unsalted butter at room temperature
1/3 cup lemon curd
1 tsp lemon juice
2 to 4 tbsp milk
1 to 1 1/2 cup confectioners' sugar
1 tsp vanilla
Cream the butter in a small bowl with a hand mixer. Add the lemon curd, lemon juice, and vanilla and beat until combined. Add 1 cup of confectioners' sugar, mixing to combine, and add milk and/or confectioners' sugar until it is the texture you like.
When the cupcakes are cool and the icing and curd are ready, cut a circle out of the center of hte top of the cupcakes (think half a wine cork) and remove the cake. Drop about 1 tbsp of lemon curd into the cupcakes and replace the cake-plug. Cover with icing to hide the seam, and place shaved lemon peel on top for garnish.
I recommend freezing a few of these, because you will want them again very soon after the first round, and not want to go to the trouble again so soon.
