Preheat the oven to 170C (fan) or 180C (conventional). Grease and line two 20cm round cake tins.
Beat butter and sugar together until pale, fluffy, and light.
Beat eggs lightly, then add gradually to the mixture. Add 1 tbsp of flour if it looks curdled.
Sift flour and baking powder, then fold gently using a spatula.
Add milk to create a soft dropping consistency.
Divide mixture between tins, level the tops, and bake for 20-25 minutes until golden and springy.
Allow cakes to cool. Spread jam on one sponge, whipped cream on the other, and sandwich together.
Dust with icing sugar and serve with tea.