Heat oven to 180C/160C fan/gas 4
and line a 12-hole muffin tin with cases.
In a large mixing bowl beat together the
butter, 175g of the sugar and the vanilla
extract until light and fluffy. Beat in the
whole egg, followed by the 4 yolks,
before briefly beating in the flour, baking
powder and milk until smooth. Divide
two-thirds of the mix evenly between
the cases, then top the centre of each
with 1 tsp jam. Divide remaining cake
mix over the top, using a wet finger to
smooth it in place so no jam is visible.
Bake for 18-22 mins until a skewer poked
into the centre comes out clean. Wait
until cool enough to handle, then transfer
the cakes to a flat baking sheet.