Make the Cake

1. Preheat the oven to 330F. Line three 8-inch pans with parchment. DO NOT GREASE.
2. Melt the butter and set aside.
3. Combine the egg yolks, half the sugar, oil, milk and vanilla in a medium bowl and whisk together.
4. Start the mixer on the medium low speed. Once the egg whites begin to foam, slowly stream in the remainder of the sugar.
5. Continue to whip on medium low speed until medium peaks form. The meringue should hold a shape but still fall over on itself in a ribbon.
6. Add the butter into the wet mix. Followed by the flours baking powder and salt- whisking just to combine.
7. Fold 1/3 of the meringue into the batter. Use a spatula to carefully fold the eggs whites into the batter. Gently fold in another 1/3 of the egg whites, followed by the final third. Make sure the batter is well combined without deflating the meringue.
8. Divide the batter into the prepared pans.
9. Bake for 28-32 minutes.

Make the Matcha Mascarpone 

1. In the mixer with the whisk attachment whip the cream to medium peaks. Sift in the matcha powder and whisk to combine. Transfer to a bowl.
2. Switch to the paddle attachment, beat the mascarpone, sugar and vanilla until creamy.
3. Fold in the whipped cream until fully combined, store in the fridge.

Make the buttercream 

1. Place a pot filled with water on the stove top and bring it to a boil. In the bowl of your stand mixer, combine the egg whites and sugar until well incorporated. Set the bowl over the saucepan whisking constantly, until it reaches 160F. Immediately remove then set the bowl onto a stand mixer fitted with the whisk attachment. Whisk on high speed until a thick and glossy, 5 to 7 minutes.
2. Switch to the paddle attachment. Slowly add the butter, a tablespoon at a time and continue beating until smooth, and silky, about 10 to 12 minutes. Add the vanilla, tonka and salt, to combine.

To assemble:

1. 1. Place one cake layer on a plate or cake board. Pipe a border of buttercream along the edge of the cake– this will prevent the filling from spilling out. Spread on half the matcha mousse, add a layer of preserves, and top with the other layer of cake. Repeat. Lightly frost the sides of the cake. Place the cake in the fridge for 20 minutes, to allow the buttercream to firm up.
   2. Frost the top and sides of your cake with the rest of the buttercream.