Step 1

Make the pastry cream 2 - 24 hours ahead of time, make double of this recipe. *See Notes*

Step 2

Let butter, milk and eggs come to room temperature before beginning

Step 3

Preheat oven to 335°F/170°C and grease your cake pans

Step 4

Split the milk into two containers, one with 1/2 cup of milk (118g) and one with 3/4 cup of milk (177g)

Step 5

Mix the 1/2 cup of milk with the vegetable oil and set aside

Step 6

Mix the remaining milk with the eggs and vanilla. Whisk together lightly and set aside

Step 7

Place the flour, sugar, baking powder and salt into the bowl of your mixer and turn on low with your paddle attachment

Step 8

Slowly add the butter, one small chunk at a time. Once it's all in it should look kind of like chunky breadcrumbs

Step 9

Add the milk/oil mixture and slowly turn your mixer up to a medium speed. Beat for exactly two minutes

Step 10

Scrape the sides of your bowl to make sure there are no lumps, then turn the. mixer back on low

Step 11

Add the milk/egg mixture slowly and mix on low until just combined

Step 12

Divide into cake pans and bake for 30-40 minutes - check to see if a toothpick comes out clean before removing from the oven

Step 13

Before you start, split the two batches of pastry cream in half and let one come to room temperature - so you should have one batch in the fridge and one batch on the counter. At the same time, bring your butter to room temperature

Step 14

Once it's at room temperature, you can start making the frosting. Place all the butter in your stand mixer and beat with a whisk attachment on high until pale and fluffy (about three minutes)

Step 15

Add the pastry cream one tablespoon at a time until it is all added

Step 16

Add the vanilla and mix in

Step 17

At this stage, taste test the buttercream to see how much sweetness you would like to add. Add the icing sugar a little at a time, whipping after every addition, until the desired sweetness is reached

Step 18

The custard buttercream should be lovely and silky smooth - if it curdles it's usually just a sign that the ingredients were not the same temperature. If this happens, just take the bowl and very gently heat the bottom of it over a bain marie and whisk until it comes together again (shouldn't take long), then return to the stand mixer and it should be beautifully silky again!

Step 19

Once completely cooled, cut each of the cakes in half so you should have four thing cake layers. I use this cake leveler, but you can also use a serrated knife

Step 20

Start building your layers, first with cake, then a layer of custard buttercream, smoothing it out as you go. Add your second layer of cake on top and put on a slightly thinner layer of custard buttercream

Step 21

On top of the thinner layer of custard buttercream, pipe a border of buttercream around the outside of the middle layer, and fill the middle with a pool of the cold custard you reserved in the fridge. Add the next layer of cake on top

Step 22

Add another generous layer of buttercream, followed by your final layer and then decorate the cake however you like!

Step 23

To get your cake looking just like mine, smooth the buttercream all over, then pipe some buttercream rosettes around the outside of the top of the cake, then use leftover custard to make another pool of custard on the top (like the middle layer)