Step 1

LEMON CURD: (Make Ahead) Roll room temperature lemons to loosen the juice inside. Then zest 7-8 lemons using a fine grater. Cut lemons and use a strainer to strain seeds from juice as you squeeze into a bowl.

Step 2

Separate the 8 egg yolks and reserve 3 whites for the cake.

Step 3

In the top of a double boiler, mix egg yolks, sugar, the 2/3 cup freshly squeezed lemon juice, and the lemon zest from all of the lemons.

Step 4

Bring the double boiler to simmer and keep it there. Simmer and whisk constantly. Both the temperature and the whisking are necessary to prevent curdling. Simmer and whisk 10 minutes in this fashion until it becomes a thick pudding-like consistency.

Step 5

Remove from heat and whisk in lemon extract. Add butter.

Step 6

Whisk until it dissolves completely.

Step 7

For a smooth lemon curd, strain the curd to remove the zest. You can leave it, though. I leave it in because I like the slight chewiness one gets from the zest.

Step 8

Once the curd is strained, it's nice and smooth like pudding.

Step 9

Pour into a bowl and cover with plastic wrap touching the curd to prevent a skin from forming. Place bowl in the refrigerator to cool completely. This will be used to make the mascarpone mousse. (My curd makes around 2 cups, and whatever the recipe makes, I use it ALL in the mousse.)

Step 10

CAKE: (Can bake the cake a day ahead.) Preheat oven to 350 degrees. Cut parchment paper to fit the bottom of a 10-inch springform pan. Spray cooking spray onto the pan. Place parchment paper in the bottom, and then spray paper too. Dust slightly with some dry cake mix.

Step 11

Mix pudding mix and cake mix. Then add 3 egg whites, 2 tablespoons of oil, and 1 1/3 cup of water until the cake mix is moist. Mix 2 minutes (according to package directions).

Step 12

Pour into springform pan. Place this into a larger roasting pan in case of leaking.

Step 13

Place into the oven for 30-40 minutes or until a toothpick inserted into the center comes out clean.

Step 14

Remove from oven and allow to cool slightly before removing springform sides.

Step 15

After removing springform sides, place the cake in the freezer for cooling. If baking the night before, I place it into the refrigerator and then place it into the freezer for about 2 hours the morning before I assemble the cake.

Step 16

LEMON MASCARPONE MOUSSE: (Should also be made several hours before assembling to help the mousse set up before assembling.) Whip mascarpone until smooth. Continue to beat while adding sugar and lemon extract.

Step 17

Check to see that sugar is dissolved. Then continue to beat while adding lemon curd. (If you stop beating while adding these ingredients, the acid of the lemon could curdle the mascarpone.)

Step 18

Add limoncello while beating. When it's smooth, chill in the refrigerator. (I do not remove all of the zest caught in the beaters or wire whip. There will still be some in the mousse.)

Step 19

LIMONCELLO SOAKING LIQUID: Combine water, sugar, and lemon zest in a saucepan. Cook over medium-low heat, stirring consistently until sugar is completely dissolved. Bring the heat up to medium-high and bring the syrup to a boil.

Step 20

Remove the pan from heat and let sit for 2 minutes. Strain the liquid to remove lemon zest.

Step 21

Stir in the limoncello and the lemon extract. Keep the syrup covered until ready to assemble the cake.

Step 22

TO ASSEMBLE THE CAKE: Remove cooled cake from the freezer. Using a bread knife, carefully split layer into two layers, cutting all of the way through. Remove top layer, carefully, to wax paper with the cut side up. Carefully, loosen the bottom of the springform pan from the bottom layer by sliding knife or spatula between parchment paper and pan bottom. Then slide cake onto a cake plate with the cut side up.

Step 23

Using a pastry brush or a spoon, put limoncello soaking liquid on each layer. (This is why I use the springform pan and cut the layers instead of using two or three round cake pans. The cut layers really allow the liquid to absorb into the cake.)

Step 24

Using half of the mascarpone mousse on the layer of cake on the cake plate, smooth it out, and then place it into the freezer until well set. If you rush this, the mousse will squeeze out when the other layer is placed upon it. Return other layers to the freezer also.

Step 25

Carefully, place the top layer onto the frosted bottom layer.

Step 26

Spread mousse along the top of the cake. You can frost the sides of the cake if you want, but I do not always do that.

Step 27

Grate white chocolate on top of the mascarpone mousse. Chill cake for several hours. It takes a while for the mousse to firm up and it's even better the day after it's assembled.

Step 28

GARNISHES: When slicing, you may garnish with fresh mint and a lemon slice. Or, it looks really great garnished with a raspberry and some raspberry sauce.

Step 29

NOTE: This can be made alcohol free by omitting the limoncello in the mousse, by increasing the sugar in the soaking liquid, and using lemon juice instead of limoncello.