Pre-heat the oven to 160°C fan (320°F) and grease and line two 8” tins.
Combine all of the dry ingredients with the soft butter (it’s important that the butter is very soft!) and mix until the butter is fully incorporated and there are no lumps, the mixture should have the texture of breadcrumbs.
Add the eggs, oil and vanilla and mix very briefly until just coming together.
Add the milk, if using a stand mixer, switch to the whisk attachment and mix on slow until the milk is incorporated then turn the speed up to medium-high and whisk for 3-5 minutes until it becomes pale, fluffy and thick, as soon as it gets thick, stop whisking, any whisking after the original thickening will overwork the gluten and knock air out! The mixture might look slightly split, don’t worry, this isn’t a problem.
Pour into the 2 tins and bake for 35-40 minutes until the sponge bounces back when pressed and a skewer comes out clean.
While the sponge is still warm, remove it from the tin and wrap it in clingfilm, this helps to trap in the moisture giving us a lovely soft and moist sponge.
