Preheat oven to 170c.
Grease and line a 20cm x 20cm (8" x 8") baking tin and set aside.
Place butter in a large bowl and melt in the microwave.
200 g salted butter
Add white sugar, brown sugar and vanilla to butter and mix to combine.
120 g white sugar, 120 g light brown sugar, 1 teaspoon vanilla
Add eggs and mix until combined.
3 eggs
Then add plain flour and corn flour and mix until combined.
275 g plain/all purpose flour, 1 tablespoon corn flour/corn starch
Mix in white chocolate chips.
150 g white chocolate chips
Pour batter in prepared tin and dollop jam on top of the batter.
100 g raspberry jam
Run the blade of a knife through the jam to create swirls in the batter.
Bake for 22 - 25 minutes or until edges are starting to brown and the center is set but still has a slight wobble.
Allow to rest for 2 - 3 hours then slice.