Preheat your oven to 325 degrees F. Spray two 8-inch round cake pans with nonstick spray, line the bottoms with parchment paper and spray again. Set aside.

In a medium size bowl, whisk together the cake flour, pistachios, baking powder, lemon zest, and salt. Set aside.

In a bowl of an electric mixer fitted with a paddle attachment, beat the butter and sugar together on medium-high speed for 3 to 5 minutes, until the texture is lighter in color and smooth in texture.

With the mixer on medium speed, gradually add the egg whites. Make sure to scrape down the sides and bottom of the bowl between additions. When all of the egg whites are added, turn your mixer to medium-high speed and beat the batter for an additional 2 to 3 minutes. At this point, the texture should be smooth and the mixture should have nearly doubled in volume.

As the batter mixes, combine the buttermilk and lemon juice.

With the mixer on low speed on low speed, alternately add the dry ingredients and the buttermilk mixture to the butter mixture, starting and ending with the dry ingredients. Scrape down the sides and bottom of the bowl to ensure all the batter has been incorporated. Stir for an additional 30 seconds.

Divide batter evenly in the two pans, about 25 to 26 ounces of batter in each 8-inch pan.

Bake the cakes until a toothpick comes out with a few crumbs inserted into the center, about 35 minutes. Let cool on wire racks for 10 minutes before inverting them onto cooling racks to cool completely.

Once the layers are cooled completely, carefully divide the cake layers in half horizontally, creating two thin layers from each cake.

Whisk the sugar, lemon zest, and lemon juice in a medium saucepan. Whisk in the whole eggs and yolks in a small bowl and then whisk them into the lemon mixture.

Cook the mixture over medium-low heat, whisking constantly, until it's thick like pudding, about 6 to 8 minutes. Remove from the heat and whisk in the butter, a few pieces at a time until incorporated.

Strain the mixture through a fine-mesh sieve into a small bowl, pushing it through with a rubber spatula. Press plastic wrap directly onto the surface to prevent a skin from forming. Refrigerate until completely set, at least 4 hours and up to 5 days.

In a medium size saucepan, heat about 2 cups of water to a soft boil and add the shelled pistachios. Boil the pistachios for about 3 minutes, drain the pistachios and spread on a clean kitchen towel.

Fold the towel over and rub the pistachios in the towel to loosen the skins. Discard as much of the skins as you can. I know it’s tedious, so it doesn’t have to be perfect.

Combine the pistachios, 1/4 cup of the milk and the sugar in a food processor. Pulse until the ingredients create a smooth paste.

In a medium saucepan, combine the remaining milk, butter and white chocolate chips. Heat on low, stirring occasionally, until the chocolate is melted.

In a high powdered blender, combine the pistachio paste and white chocolate mixer. Blend until smooth and creamy. If you need to adjust the consistency, you can add a couple splashes of milk.

Let the pistachio mousse reach room temperature before folding in the heavy whipping cream.

For the heavy whipping cream: In a stainless steel bowl, beat the heavy whipping cream with the whisk attachment until stiff peaks form.

Fold the whipped cream into the pistachio mousse.

In the bowl of an electric mixer fitted with the paddle attachment, beat the butter and cream cheese for about one minute.

With the mixer on low speed, gradually add the sifted powdered sugar, followed by the pistachios, lemon zest, lemon juice, heavy whipping cream and pinch of salt.

Turn the mixer on medium-high speed and beat for about 3 to 5 minutes, until light and fluffy.

Remove the bowl from the mixer and mix the frosting by hand with a wooden spoon to push out any air bubbles.