Olive Oil Layer Cake with Lemon Curd and Rosemary Buttercream

OLIVE OIL LAYER CAKE

1. Preheat the oven to 350°f / 180°c. Grease three 6” cake pans, and line with parchment paper rounds.
2. In a large bowl, whisk together the sugar, flour, cornmeal, salt, baking powder, and baking soda. In a medium bowl, whisk together the olive oil, whole milk, eggs, vanilla bean paste, and lemon zest.
3. Add the wet ingredients to the dry ingredients, and whisk together until combined. Finish with a rubber spatula to ensure that there are no dry parts at the bottom of the bowl.
4. Divide the batter evenly between the three pans. Bake for 40 to 45 minutes, until a skewer inserted into the middle of the cake comes out clean. Transfer to a wire rack and cool for 10 minutes, then remove from pans, peel parchment from the bottom, and allow to cool completely. These can be made ahead - store tightly wrapped in plastic until ready to use if making ahead.

MEYER LEMON CURD

1. Place a heatproof bowl over a pot of simmering water, ensuring that the water does not touch the bottom of the bowl. Combine all of the ingredients, whisking often. Watch the edges of the mixture carefully to ensure that it does not catch and go lumpy, switching to a flexible rubber spatula as needed to help clear the sides of the bowl.
2. Heat, stirring often, until the mixture is thick enough that when you coat the back of a spoon or spatula with curd, you can drag a finger through it, and leave a clear track. Once it is at this point, continue to cook for a further 5 minutes. It will thicken more when it cools. Transfer to a bowl or container, straining through a sieve if you can see any small pieces of egg, then press a piece of plastic wrap directly against the surface of the curd. Place in the fridge to cool completely.

ROSEMARY GERMAN BUTTERCREAM

1. In a medium saucepan, heat the milk to just shy of a simmer.  Remove from the heat, add the rosemary, stir well, and steep for 30 minutes. Strain through a very fine mesh sieve, and re-weigh the infused milk and top up to 190g. Wipe out the saucepan, and return to the milk mixture to the heat. Bring to just shy of a simmer. Meanwhile, In a bowl, whisk together the sugar and corn starch to remove any lumps, then add the egg, egg yolk, salt, and vanilla bean paste.
2. Using one hand to whisk constantly, pour half of the hot milk mixture into the egg mixture. This helps to temper the eggs and stop them from scrambling. Whisk until incorporated, and then pour the whole lot back into the saucepan.
3. Heat the milk and egg mixture over medium heat, whisking constantly, until it begins to bubble. It will thicken quickly. Once it has thickened, cook for one minute, then remove from the heat. Pour into a shallow container or bowl of a stand mixer and press some plastic wrap over the surface to avoid a skin from forming. Refrigerate until cold - at least four hours, preferably overnight. If you need to speed this process up, you can place the pastry cream in a bowl, then place the bowl in an ice bath, or use a shallow container. Stir frequently.
4. Fit your mixer with the whisk attachment, and place the pastry cream in the bowl. Whip the mixture on medium until creamy and lump-free. Begin adding the butter, a few cubes at a time, until fully incorporated. It may look curdled at some point but just keep whipping - it will come together! Whip for a further 2 minutes.

FILLING AND ASSEMBLY

1. If the cakes domed in the oven, level them a little with a sharp bread knife. Transfer some of the rosemary buttercream to a piping bag fitted with a medium round tip - this will be used to make a buttercream dam to hold in the lemon curd between the layers.
2. Secure one of the layers of cake to a cake turntable or cake stand using a little buttercream. Add about half a cup of rosemary buttercream onto the first layer of cake, and smooth using an offset spatula. Create a buttercream dam using the buttercream in the piping bag by piping a ring around the outside edge of the first layer. Fill in the ring with approximately 6 Tbsp of the lemon curd. Place the second layer of cake onto the first, pressing very lightly to secure, and sealing the joins with a thin layer of buttercream. Repeat the layering process - add half a cup of buttercream, make a dam, fill with 6 Tbsp lemon curd, then top with the third layer of cake - I like to put this one upside down to ensure that the top of the cake is flat.
3. Coat the sides of the cake by applying a thin layer of buttercream over the surface of the cake, and smoothing with a bench scraper or icing smoother. I gave this cake a semi naked look - so added buttercream to the sides, then scraped off to get my desired look. Smooth the top edge of the cake using an offset spatula.
4. Add flowers as desired (see notes about making flowers safe to use on cakes), and refrigerate until ready to serve. Remove from the fridge about an hour before serving to allow it to come to temperature.
5. Store leftovers in an airtight container.