Step 1

Preheat oven to 350 degrees. Spray or butter and flour three 9-inch round baking pans. Line bottoms with a parchment round, set aside.

Step 2

In a food processor, pulse 1 1/4 cups pistachios until a finely ground powder forms.

Step 3

In a medium mixing bowl whisk together the ground pistachios, flours, baking powder, baking soda, and salt.

Step 4

In the bowl of a stand mixer, beat butter on high until smooth and creamy, about 2 minutes. Add sugar and beat for 2 minutes on high. Add vanilla, almond and egg, mix until combined.

Step 5

With mixing speed on low, alternate adding dry ingredients and the milk and cream. Mix until a few dry streaks remain.

Step 6

In a medium mixing bowl, using a hand mixer, beat 3 egg whites and cream of tartar until stiff peaks form. Using a rubber spatula, gently fold into the batter until incorporated.

Step 7

Divide the batter evenly between the prepared pans. Place in the oven and bake for 35-40 minutes or until the top springs back when touched.

Step 8

Remove from the oven and allow to cool in the pans for 15 minutes before inverting onto a wire rack to cool completely.

Step 9

Meanwhile, to make the frosting, in the bowl of a stand mixer, beat butter on high until creamy, about 2 minutes. Add vanilla, salt and powdered sugar, mix until combined. Add mascarpone and mix on low for 10 seconds, then fold by hand until a smooth, creamy frosting forms.

Step 10

To assemble the cake, 1/4 of the frosting between the first layer, a 1/4 of the frosting between the second layer, and spread the remaining frosting over the top and down the sides of the cake. Chop the reserved 1/4 of pistachios and sprinkle on the top edges. Add a pinch or two of large sea salt flakes before serving.