Preheat the oven at 160ºC conventional oven and prepare 3 x 20 cm baking pan with parchment paper.

Sift together the all-purpose flour, baking powder, baking soda, and salt. Add the lemon zest and poppy seeds to the flour mixture, mix it together, and set it aside. Mix together the buttermilk and vanilla extract and set it aside.

In a mixing bowl, use the paddle attachment add the butter, vegetable oil, and sugar and mix it on high speed for 3 min.

Add the eggs one at a time into the mixture and mix it in until combined.

Add the lemon juice to the milk. It will curdle but don’t stress, it’s just the lemon juice reacting with the milk.

Continue by alternating between adding ⅓ of the flour mixture and ½ of the milk mixture, ending on the flour mixture. Mixing in each addition until just combined.

Divide the cake batter into the 3 prepared 20 cm baking tins and bake them for 26-28 min or until a cake tester comes out clean.

Let the cakes cool on a cooling rack. After 5 min, gently remove the cake from the cake tin and let the cakes cool down completely.

Then take it off the heat, and pour it through a sieve over a bowl, to catch any cooked egg bits.

Let it sit for 2 mins to slightly cool down. Then add the cold cubed butter and with an emersion blender, blend it together until smooth. Pour the curd into a shallow bowl, so it cools down faster, and cover the curd with a piece of cling film so it touches the surface or the curd and place it in the fridge. Let it cool down until cold, about 1 hours.

Melt the white chocolate and heavy cream together over a bain-marie or in the microwave. Let it cool down to room temperature (it’s important that it’s not too hot) while making the buttercream.

Take the butter out of the fridge 10 min before starting. Cut the butter into cubes.

Sift the powdered sugar.

In your stand mixer, use the paddle attachment, start by creaming the butter for 2 min on medium speed. Scrape down the sides of the bowl and mix 1 min more. Add the melted white chocolate and mix it in until incorporated. Scrape down the sides of the bowl and give it another mix to make sure it’s fully incorporated with the butter. On low speed, add the sifted powdered sugar in 3 portion, mix in the powdered sugar at low speed, until each addition is fully incorporated. Scrape down the sides of the bowl, and mix for 2 min on low/medium speed.

Take the bowl off the stand mixer and with a rubber spatula or wooden spoon, beat it well by hand to make sure to remove the air bubbles in the buttercream.

Add ⅓ of the buttercream to a piping bag with a closed star piping tip, e.g. 2D, and set it aside.

Place the first cake layer on your serving dish or cake board on your turntable. If you don’t have a turntable, don’t worry, you can easily decorate the cake without it.

Add a very thin layer of buttercream to the cake layer and with an offset spatula, even it out. Pipe a boarder around the top of the cake. Then add half of the lemon curd and even it out. Add the next sponge layer and do the same as the previous layer. Then add the layer cake layer and cover the cake in a thin crumb coat. Place it in the freezer for 30 min, for the buttercream to set.

Add the remaining buttercream, but the buttercream in the piping bag save that for the decoration, and spread it out in an even layer. Scape down the sides of the cake to get smooth sides on the cake. Place it back in the freezer for 30-60 min. Meanwhile make the ganache for the decoration.

Chop the white chocolate if you’re not using chocolate chips.

Heat the heavy cream to a boil and pour it over the chocolate. Let it sit for 2 min. Then stir it together with a rubber spatula until smooth. Add the white and yellow gel color and mix it well together. Let it cool down until around room temperature. You don’t want it too warm as it otherwise can melt the buttercream.

Then take the cold cake out of the freezer and pour the ganache over the cake so it create a drip effect. Even the top out with an offset spatula or a spoon.

Lastly decorate with the remaining buttercream and sprinkle with poppy seeds.