Lemon Blueberry Cupcakes with Vanilla Bean Buttercream

Photo by Katie Kay

I've been craving Lemon Blueberry for a month.  There's something about it that screams BRING IT ON, SPRING!  We've had an unseasonably long winter and I'm more than ready for toasty heat, short shorts, and flip flops.  What better way to prepare my body for those short shorts than to whip up 30 cupcakes 2 weeks in a row?  Exactly.
I put a spin on my favorite Lemon Layer cake recipe.  You might remember this one as the birthday cake I made for Matt the year he wanted his mom's Chocolate cake with vanilla frosting.  I vetoed that because I had a BETTER idea (in my opinion.)  I'm a cruel wife.
I made these cupcakes last weekend for a joint birthday party for my mom, grandpa, and uncle.  You've never seen grown-ass people scarf down 3 cupcakes at a time so fast in your life, I guarantee.  My dad and uncle didn't even get one.  Move faster!  No sympathy here.  Eat or be eaten.
They were such a hit that I decided to make them again this week and take them to my super awesome co-workers who worked really hard during a hectic week.  I promised them a treat, and given that we have an office of 6 people, I think I'll have just a couple leftover since this recipe makes 30.
I made the regular lemon cake batter, then I separated 1/3 of the batter and put it in a different bowl, then mixed it with about 1/4 cup blueberry preserves.  I put a dollop of the blueberry batter on the top of each muffin tin without mixing or stirring it, and baked them just like that.  They marbled perfectly!

Photo by Katie Kay

The original recipe calls for candied lemon slices as decoration, so I used my leftover simple syrup and mixed in 2 Tbsp blueberry preserves, then basted the syrup on the tops of each baked cupcake.  This gave them a prettier purple color and contrasted well with the white frosting.
The last adjustment to the recipe that I made was to use a filling tip to fill each cupcake with lemon mascarpone.  I squeezed generously until I saw the mascarpone oozing out of the top.  I broke an unfrosted cupcake in half to see how much filling they had, and I think they still could have used more.  I felt like I put a LOT in them, so be generous with your squeezing!
Below you can see the blueberry simple syrup basted on the top.  Isn't it pretty?  And the blueberry marbling throughout the cupcake is light, but attractive.  And you can see the lemon mascarpone filling in the middle.

Photo by Katie Kay

Lemon Blueberry Cupcakes with Vanilla Bean Buttercream and Lemon Mascarpone filling
Cupcakes: 3 cups cake flour 1 Tbsp baking powder 1/2 tsp salt 2 sticks butter, softened 1 lemon, zested 2 cups sugar 5 eggs, room temperature 1 1/4 cups buttermilk, room temperature 1 Tbsp lemon extract 1 tsp vanilla extract 1/4 cup blueberry preserves
Filling: 4oz mascarpone, cold 2 1/2 Tbsp butter, softened 1 1/4 cup powdered sugar 2 tsp lemon extract 1 lemon zest 1 cup heavy cream
Frosting: 4 sticks butter, softened 4 cups powdered sugar 1 vanilla bean, split and seeds removed 2 tsp vanilla extract 2 Tbsp heavy cream
Candied lemons: 2 lemons, sliced thin 1 cup sugar 1 cup water 2 Tbsp blueberry preserves
Preheat oven to 350 and line 30 muffin tins with paper liners.  In a medium bowl, combine cake flour, baking powder, and salt.  Whisk gently to combine.  In a mixer bowl, add softened butter and beat 2 minutes until light and fluffy.  Add lemon zest and sugar, and beat until combined.  Add eggs one at a time and mix until combined.  Add lemon extract and vanilla to the buttermilk.  Add flour mixture and buttermilk to the bowl, starting with dry ingredients and alternating between wet and dry until combined.
Scoop 1/4 of the batter into the flour bowl (save a dirty dish!) and add the blueberry preserves.  Fold with a spatula until no streaks remain.
Fill 30 muffin cups 1/2 full with yellow batter.  A spoonful at a time, drop a dollop of the blue batter on top of each.  No need to mix or stir, just stick it in the oven for 18 minutes, or until toothpick inserted in the center comes out clean.
While the muffins are baking, add mascarpone and butter to a mixer bowl and beat until soft, then slowly add powdered sugar. Add lemon extract and zest, then beat until combined.  Pour mixture into a separate bowl, then clean out mixer bowl, add cold cream, and whisk on medium high until peaks form.  Add 1/2 of whipped cream to the mascarpone and fold with a spatula gently until combined.  Repeat with remaining whipped cream.  Set aside.
To make the frosting, add butter to mixer bowl and beat until soft and creamy.  Slowly add powdered sugar.  Split vanilla bean lengthwise and scrape seeds out and add to frosting.  Add vanilla and combine.  Add cream as needed for desired texture.
By this time, muffins should be out of the oven and cooling.  Start your candied lemons since they take a while, and then we'll fill and frost our cupcakes.  Add 1 cup of water and 1 cup of sugar to a skillet with a wide base.  Turn on medium heat and whisk gently until sugar dissolves.  Add thinly sliced lemons in 1 layer, and let cook on medium-low heat for 20-30 minutes.  Turn off heat and let them sit until you need them.
To fill cupcakes, I used a metal cupcake filler tip.  It's long and very skinny and comes with most standard decorator tip sets.  Add the mascarpone to a decorator bag with the filling tip at the end, and push tip down into each cupcake, gently squeezing bag until you see filling reaching the top of the cupcake.
Remove candied lemons from pan and add blueberry preserves to the sugar/water mixture.  Stir with a fork until combined, then baste the top of each cupcake generously with the blueberry simple syrup.
Frost cupcakes with vanilla bean frosting, and top with candied lemon slices and a blueberry.  You can quarter or halve your lemon slices.
Store in the fridge, but bring to room temperature before serving.