Gently melt your butter in your saucepan over a low heat.
Set aside to cool for 10 minutes until tepid.
Add your sugars to your cooled butter and mix thoroughly with a spatula or wooden spoon.
Add your eggs and vanilla essence and mix thoroughly.
Mix your flour, baking powder, cornflour and salt together separately.
Add your flour mixture to the wet mixture and mix thoroughly.
Scrape down your bowl with a spatula to ensure the mixture on the sides and base are fully mixed in.
Tip in your white chocolate chips and mix in.
Tip your blondie mixture into your prepared tin and level out with the back of a desert spoon.
Warm your jam in a microwave to ensure it is a little runny, but not hot. 10-15 seconds should be enough.
Blob your jam onto the mixture in rows of 3, ie 9 blobs.
Take a skewer (or butter knife or cocktail stick) and roughly spread the jam around the surface of the mixture to create a marble effect.
Pop on your mini Jammy Dodgers, in rows of 3, ie 9 dodgers in all.
Place in the centre of your oven and bake for 25 minutes.
The blondies are ready once the surface has turned golden brown and a skewer comes out with just a few fudgy crumbs on it.