Preheat the oven to 180°C (160°C fan-forced). Grease and line the bases of two 20cm sponge pans.
1. Beat the butter and sugar in a small bowl with an electric mixer until pale and fluffy. Add the vanilla and eggs and beat for another minute. Gently fold in the sifted flour and milk in two batches.
2. Spoon into the prepared pans, level the surface and bake for 20 minutes. Cool the cakes in the pans for 15 minutes before turning onto a wire rack to cool.