Lemon Mascarpone Cake

This is my birthday cake this year and it was really quite delicious!  Especially the frosting.  The cake can be a bit hard to cut because the icing is so soft and the cake pretty dense.  Beware, but it is all delicious.

LEMON CURD

• 1/4 cup (60ml) fresh lemon juice (about 1–2 lemons)
• 2 tsp finely grated lemon zest
• 1/3 cup (69g) sugar
• 4 egg yolks
• 3 tbsp (42g) salted butter

LEMON CAKE LAYERS

• 3/4 cup (168g) unsalted butter, room temperature
• 1 1/2 cups (310g) granulated sugar
• 3/4 cup (173g) sour cream
• 1 tsp vanilla extract
• 1 1/2 tbsp finely grated lemon zest
• 6 egg whites
• 2 1/2 cups (325g) all purpose flour
• 4 tsp baking powder
• 1/2 tsp salt
• 1/2 cup (120ml) milk
• 2 tbsp (30ml) water
• 6 tbsp (90ml) fresh lemon juice

WHIPPED MASCARPONE FROSTING

• 2 1/2 cups (720ml) heavy whipping cream, cold
• 1 1/2 cups (173g) powdered sugar
• 2 tsp vanilla extract
• 16 oz (452g) mascarpone cheese, chilled*

Instructions

TO MAKE THE LEMON CURD:

1. Combine all the ingredients in a double boiler (or in a metal bowl over a pot of simmering water). Heat while whisking constantly until mixture thickens and reaches 160 degrees, or coats the back of a spoon.
2. Pour the lemon curd into a heat proof bowl, cover with clear wrap pressed onto the the top of the curd to avoid a film developing, and refrigerate until cold.

TO MAKE THE CAKE LAYERS:

3. Preheat oven to 350°F (176°C) and line three 8 inch cake pans with parchment paper and grease the sides.
4. Cream the butter and sugar together until light and fluffy, 3-4 minutes.
5. Add the sour cream, vanilla extract and lemon zest and mix until combined.
6. Add the egg whites in two batches, mixing until well combined after each. Scrape down the sides of the bowl as needed to make sure all is incorporated and smooth.
7. In a separate bowl, combine the dry ingredients. In another small bowl or measuring cup, combine the milk, water and lemon juice.
8. Add half of the dry ingredients to the batter and mix until well combined. Add the milk mixture and mix until well combined. Add the remaining dry ingredients and mix until well combined. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
9. Divide the batter evenly between the three 8 inch pans and bake for 23-25 minutes, or until a toothpick inserted comes out with a few crumbs.
10. Remove the cakes from the oven and allow to cool for about 2-3 minutes, then remove to cooling racks to cool completely.

TO MAKE THE FROSTING:

11. Add the heavy whipping cream, powdered sugar and vanilla extract to a large mixer bowl and whip on high speed until soft peaks form.
12. Add the mascarpone cheese to the whipped cream and whip until stiff peaks form. It will happen fairly quickly. Set whipped frosting in the refrigerator.
13. To assemble the cake, use a large serrated knife to remove the domes from the top of the cakes.
14. Place the first layer of cake on a serving plate or a cardboard cake round. Pipe a dam of frosting around the outside of the cake. I use Ateco tip 808 for the dam so that it’s tall.
15. Spread half of the lemon curd evenly on top of the cake layer, inside the dam. It should fill the dam about half way full.
16. Add some mascarpone frosting to the top of the lemon filling and spread into an even layer to fill in the remaining dam space.
17. Add the second layer of cake and repeat the filling layer with the remaining lemon curd and additional mascarpone frosting.
18. Add the final layer of cake on top, then smooth out the frosting around the sides of the cake.
19. Frost the outside of the cake, then use an offset spatula to create a striped pattern on the sides of the cake, if desired. Pipe swirls of frosting onto the top of the cake and finish it off with some lemon slice candies and white pearl sprinkles.
20. Refrigerate well covered until ready to serve. I find that the cake is best when served a little chilled, but not cold. Cake should stay fresh when well covered for 2-4 days.
*I prefer to use the mascarpone cheese when still chilled, but soft, so that it’ll in corporate well, without chunks. The warmer mascarpone cheese is, the more likely it is to soften to the point that it won’t firm up well again and can make too soft of a frosting.