Prepare the tins and oven. Preheat your oven to 180°C (160°C fan). Grease three 20cm round cake tins and line the bases with a circle of parchment paper. This ensures your layers will release cleanly, a crucial first step for pristine plating.

Whisk the dry ingredients. In a large bowl, whisk together the flour, sugar, baking powder, and salt until fully combined. You should see a uniform, pale mixture with no lumps of baking powder. This aerates the flour, giving the cake a lighter start.

Combine the wet ingredients. In a separate jug or bowl, whisk the milk, eggs, vanilla bean paste, and oil until the mixture is homogenous and slightly frothy on top. The oil is our secret weapon for a moist, tender crumb that stays soft for days.

Create the batter. Add the softened butter to the dry ingredients. Using a hand mixer or stand mixer on low speed, mix until the butter is broken into small, pea-sized pieces coated in flour. It will look like coarse sand.

Add the wet mixture. Pour the wet ingredients into the flour-butter mixture. Mix on low speed for 30 seconds, then increase to medium speed for a full 2 minutes. The batter will transform from lumpy to smooth, thick, and glossy. You’ll smell the sweet vanilla and see a pale, satiny sheen. Scrape the bowl well.

Divide and bake. Divide the batter evenly between the three prepared tins. Gently tap each tin on the worktop to release any large air bubbles. Bake for 25-30 minutes. The cakes are ready when they are a deep golden brown, the tops spring back firmly when touched, and a skewer inserted into the centre comes out clean with only a few moist crumbs clinging to it.

Cool completely. Let the cakes cool in their tins on a wire rack for 10 minutes. The edges will pull away slightly from the tin. Turn them out onto the rack, peel off the parchment, and let them cool completely. This is essential; warm cake will melt your buttercream into a sad puddle.

Make the buttercream. In a clean bowl, beat the softened butter on medium-high speed for 5-7 minutes until it is pale, fluffy, and almost white. The sound will change from a heavy slosh to a light, airy whoosh. Reduce speed to low, add the sifted icing sugar in three additions, then add the milk, vanilla, and salt. Once combined, beat on high for 2-3 minutes until silky smooth and spreadable.

Assemble for impact. Place one cooled cake layer on your serving plate or a cake board. Spread a generous layer of buttercream on top. Repeat with the second layer. Place the third layer on top, flat side up. Apply a thin "crumb coat" of buttercream all over the cake and chill for 20 minutes. This traps any loose crumbs for a flawless final finish. Then, apply a thick, final layer of frosting, using a bench scraper for sharp, clean edges.