Diplomat Cake

Amanda Hearty's diplomat cake shows off the simple flavours of vanilla, butter and sugar in a not-so-simple and delightful layering of textures from crunchy to creamy to fluffy.
By | October 25, 2015



6 eggs, large
2 egg yolks (save whites for butter cream)
1 ¼ cups sugar
1 ½ cups all-purpose cake flour

In a medium pot, fill 1/3 water and bring to a simmer. Using a mixing bowl that fits over the pot, heat the eggs, egg yolks and sugar. Stir the mixture until it feels warm to the touch. Place the warm mixture into a stand mixer and whip on high for 7 to 10 minutes. The mixture is ready when it has become a very pale yellow. When you lift the whip out of this mixture, it should fall on top on its self and rest for a few seconds before sinking into the bowl. Gently fold in sifted flour in 4 to 5 stages. Be careful not to deflate the batter, and always scrape the bottom and sides of bowl to make sure there are no flour lumps. Gently pour the Genoise in a greased and floured 10" cake pan. Preheat oven to 375 F for 30 to 40 minutes, or until the centre springs back like a sponge when touched.

*notes: Heating the eggs relaxes the protein and allows you to maximize the amount of air you can whip into it. A Genoise does not contain baking powder or baking soda to help it rise. The leavening in this cake is all air! When the air hits the high heat of the oven, it expands and makes the cake rise. This is why you need to be very gentle when folding in the flour! The Genoise can be made up to two weeks ahead of time, wrapped and frozen.

Puff Pastry

5 cups all purpose flour
2 teaspoon salt
2 cups of water
1 lb unsalted butter

Add flour, salt and water to mixing bowl. Mix on medium speed for 5 minutes. Shape dough in a square. Cover with plastic chill for at least one hour. While the dough is resting, shape the pound of butter into an 8' square and chill for at least one hour. After the dough has chilled for at least an hour, remove the dough. Dust your work surface with flour and roll the chilled dough into a square to about 10 to 12'. Remove the chilled butter and place it into the center of the dough. Pull each corner of the dough over the butter. The butter should be completely covered in dough at this point. Roll the dough and butter into a rectangle about three times its original size. Fold one third of dough down over the center of the rectangle, and then the other third over the top to close it. Wrap and chill for at least one hour. Repeat this step 3 more times, chilling in between each step. Roll the finished dough out to about 3mm. Using a knife, cut the dough into a rectangle big enough to cover your baking sheet. Use a fork to poke holes in the dough to avoid giant air bubbles. Bake at 375 F for approximately 30 to 40 minutes. Don't be afraid to give your puff pastry alot of colour, that's where the flavour comes from! Cut out a 10' circle once puff has cooled. Save leftovers to coat the outside of the cake.

Pastry Cream

2 cups milk
¾ cup sugar
4 egg yolks (save whites for butter cream)
¼ cup cornstarch
1 teaspoon vanilla

In a pot over medium heat, start to warm milk. While milk is heating, add sugar, cornstarch and egg yolks into a mixing bowl. Whisk well. Temper the egg yolk mixture by slowly pouring the hot milk into it while constantly whisking. Pour the entire mix back in the pot and place on high heat and whisk until it comes to a full boil. Once it comes to a full boil, add vanilla and transfer to a clean dish. Cover with plastic wrap and place in the fridge for up to 3 days.


6 egg whites
1 ½ cups sugar
1 lb butter
2 tablespoons vanilla extract

In medium pot, add 1/3 water and bring to a simmer. Add egg whites and sugar into a mixing bowl. Heat egg mixture over the water bath, until the mixture feels warm to the touch. Add into a stand mixer and mix on high speed for 7 to 10 minutes. It's ready when it looks like a white meringue and cool is enough that the butter will not melt. On medium to high speed, add butter in pieces. Add vanilla. Buttercream can be stored in the fridge for up to 7 days.

Simple syrup

½ cup sugar
½ water
2 tablespoons rum or vanilla

Bring sugar and water to the boil, making sure sugar is dissolved. Add rum or vanilla. Simple syrup can last in the fridge for weeks at a time. Any leftover syrup can always be added to your coffee. :)

Cake Assembly

With a serrated knife, slice Gennoise into 2-3 pieces. Brush Genoise with simple syrup until very moist. Add the pastry cream, butter cream, and puff in alternate layers. Finish the outside of the cake with crushed puff pastry.

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