Step 1

Preheat the oven to 325 degrees F. Prepare three 8-inch or four 6-inch round cake pans with non-stick spray, parchment paper on the bottom of the pan, and another coat of spray. Set aside.

Step 2

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

Step 3

In the bowl of a stand mixer, fitted with the paddle attachment, beat the butter, oil, and sugar on high until fluffy and smooth, about 5 minutes.

Step 4

Add the eggs and the egg whites, one at a time to the bowl and beat on medium until well incorporated.

Step 5

Turn the mixer on low and add 1/3 of the flour mixture to the butter mixture and mix until fully incorporated. Then add half of the buttermilk and blend well, followed by another 1/3 of the flour mixture, the second half of the buttermilk and lastly, add the remaining flour mixture and mix until incorporated.

Step 6

Add the vanilla bean paste and beat on low until incorporated. Scrape down the sides of the bowl and mix on low for another 30 seconds.

Step 7

Evenly distribute the cake batter among the three 8-inch or four 6-inch pans and bake for 25 to 30 minutes, until toothpick comes out with just a few moist crumbs on it.

Step 8

Remove cakes from the oven and let cool in pans for 10 minutes before inverting onto cooling racks.

Step 9

When cakes are completely cooled, I like to wrap each cake layer individually with plastic wrap and stick it in the refrigerator or freezer until I’m ready to frost. The cake will be easier to work with if it’s cooled a bit. If I’m making the cake a day or two before I actually need to frost it, I put it in the freezer to ensure freshness. If I’m frosting same-day, I’ll just put it in the refrigerator to chill until needed.

Step 10

TOASTED MACADAMIA NUTS (plan to do ahead of time): Roughly chop the macadamia nuts and then place in a saute pan over medium heat with the salt. Toast the macadamia nuts until golden brown and fragrant, making sure to stir frequently.

Step 11

Once the macadamia nuts are toasted, combine the toasted macadamia nuts and nut milk (or water) in a bowl and cover with plastic wrap. Let the nuts soak for about an hour.

Step 12

After the nuts have soaked for an hour, place the nuts and nut milk in a blender or food processor. Puree until smooth.

Step 13

MACADAMIA NUT MILK (plan to do ahead of time): Using a cheesecloth or thin dish towel, strain the liquid from the puree. This is best done over a large bowl. Pour the nut puree over the cheesecloth and squeeze the liquid through the cloth. We want to get 1 cup of liquid from our puree. If you've strained as much as possible and still don't have 1 cup of liquid, place the leftover paste from the cheesecloth back into your blender or food processor, add another 1/2 cup of nut milk and puree again. You'll then strain the puree again to get more liquid.

Step 14

The nut milk can be made up to a week before you plan to make the custard. Just make sure to refrigerate the milk in a mason jar or other airtight container.

Step 15

FOR THE CUSTARD (plan to do ahead of time): In a medium-sized mixing bowl, whisk the sugar and egg yolks. Add the cornstarch and whisk until the mixture is light yellow and a bit thick.

Step 16

In a medium saucepan, heat 1 cup of the nut milk and vanilla. Just before the milk begins to boil, remove it from the heat.

Step 17

Very slowly, add the nut milk to the egg mixture, whisking constantly to avoid curdling the eggs. When you’ve combined all the nut milk with the egg mixture, pour the mixture back into the saucepan and return to the stove.

Step 18

Cook the mixture over medium heat until it has thickened, about 10 to 15 minutes. Make sure to stir frequently. Allow the custard to cool completely and then place in an airtight container to refrigerate overnight.

Step 19

TO COMPLETE THE MACADAMIA NUT CREAM FILLING (finish day of assembly): Beat the heavy whipping cream to stiff peaks. Fold the heavy whipping cream into your custard. Best used right away.

Step 20

In the bowl of a stand mixer fitted with the paddle attachment cream the butter on medium speed for about 3 minutes, until the mixture is light and fluffy.

Step 21

With the mixer on low speed, slowly add the powdered sugar, followed by the heavy cream, vanilla bean paste, and dash of salt.

Step 22

Continue to beat the frosting on medium-high speed for an additional 5 minutes.

Step 23

Before frosting your cake, mix the frosting by hand with a wooden spoon to push out the air pockets.

Step 24

Chop the macadamia nuts and then place in a saute pan over medium heat with the sugar.

Step 25

Cook the macadamia nuts until the sugar has melted, coated the nuts and the nuts become golden brown. Make sure to stir frequently. Once the nuts are cooked, spread them out on parchment paper to cool completely.

Step 26

Place the first cake layer, top side up (top side up), on a cake board or cake plate. Using an offset icing spatula, spread a thin layer of frosting over the cake layer, about 1/2 cup. This creates a barrier between the cake and filling so the cake doesn't become soggy.

Step 27

Pipe a rim of frosting around the edge of the cake layer. This will help support the cake layers and prevent the filling from spilling out.

Step 28

Spread about 1/2 to 2/3 cup cream filling on the cake layer.

Step 29

Sprinkle about a 1/2 cup of the toasted macadamia nuts over the cream filling.

Step 30

Gently place the second cake layer on top of the fillings and the above steps for the second layer.

Step 31

Place the final cake layer top side down on the second layer of fillings.

Step 32

Freeze the cake for about 10 minutes to help set the frosting and filling, making it a bit more stable for when you frost. If the cake still feels wobbly, add a dowel to the center of the cake (or you can even use drinking straws for this).

Step 33

After the filling is set, use a small amount of frosting to apply a crumb coat around the entire cake. Freeze the cake again for another 10 to 15 minutes to set the crumb coat.

Step 34

After the crumbs are locked in, continue to frost and decorate the cake with the remaining frosting and toasted nuts.