Preheat the oven to 350F/177C convection (325F/163C conventional) and grease and line three 6 inch cake pans.

In a medium bowl, whisk together the flour, baking powder and salt until they're evenly distributed.

Place the room temperature butter, the oil and the granulated sugar in a large bowl and use an electric mixer with the whisk attachment to beat them for 2 minutes.

Add the eggs, one at a time, beating on medium speed until each egg is fully incorporated. Add the sour cream and vanilla extract and beat just until combined.

Add half of the dry ingredients to the wet ingredients, turn the mixer on low speed and then pour in the milk, followed by the rest of the dry ingredients.

Distribute the batter evenly among the three cake pans, about 14oz in each pan and bake for 30-35 minutes. When the cake is fully baked it will release itself from the edge of the pan and it will spring back if you press on the center of it.

Allow the cake to cool completely before frosting.

In a medium bowl, combine the egg yolks, sugar, salt and cornstarch. Whisk them together until the mixture is smooth; set aside.

In a medium saucepan, over low-medium heat, bring the milk to a simmer and then slowly stream the milk over the egg mixture, while whisking continuously.

Return the whole mixture to the pot and over low-medium heat, whisk continuously for a 1-3 minutes until it starts to thicken.

Now whisk aggressively for another 30-60 seconds and then remove the cream from the heat and pour into a bowl (pour through a sieve if it's lumpy)

Add the butter and vanilla and allow it to melt from the heat of the pastry cream. It'll separate at first but as you whisk it, it'll come together and be nice and smooth.

Cover the surface of the custard with plastic wrap and allow to cool to room temperature.

Gently whisk it again when you're ready to use it.

Place the egg whites and granulated sugar in the bowl of a stand mixer. Bring a small pot with 1/2 cup of water to a boil and lower the heat to simmer.

Place the bowl of egg whites and sugar on top of the simmering water for 5-10 minutes, whisking intermittently, until the granulated sugar is completely dissolved.

Once the sugar is dissolved, remove the bowl of egg whites from the heat and use an electric mixer with a whisk attachment to beat the egg whites with the sugar. Beat for 7-10 minutes on high speed and then lower the speed to low-medium.

Slowly add 2 Tbsp of butter in at a time. Wait for the butter to incorporate before adding the next chunk. Once all the butter is added, turn the mixer up to high speed for 10-15 seconds.

Line a cook sheet with aluminum foil and set aside.

Place the sugar and water in a medium size, heavy bottom sauce pan. Swirl the pan until the sugar is immersed in water. Place the saucepan over low-medium heat and allow the sugar to fully dissolve in the water.

Bring the sugar to a gentle simmer and place the lid on the pan until the color begins to darken to a light amber color. This may take 5-10 minutes, make sure to remove the lid every couple minutes to check the color. You can gently swirl the pan if the color change is uneven but do not stir it.

Once the color is a nice amber color, pour it over the prepared pan and allow it to cool to room temperature. Once it's fully cooled, use a knife to stab the caramel so it shatters into pieces (do this right when it's cooled, don't leave it out for a long time).

Store left over shards in an airtight container/bag in the freezer.

Place the first layer of cake onto a flat surface. Top with a couple Tbsp of granulated sugar and then use a culinary torch to caramelize the sugar on top of the cake.

Use a piping bag fit with a round tip to pipe a border of Swiss meringue buttercream around the edge of the cake layer.

Use half of the pastry cream to fill inside the buttercream border. Generously top the pastry cream with caramel shards (put more than I did in the photos).

Repeat this with the second layer of cake and then top with the third layer. Refrigerate the cake for 20-30 minutes to set before frosting the outside.

Use the rest of the buttercream with an offset spatula and cake scraper to frost the outside of the cake. Top with additional caramel shards.

Creme Brulee Cake is best served at room temperature or slightly chilled.