Blackberry Blondies

200g unsalted butter
150g 35% white chocolate
300g light muscovado sugar
3 large eggs
200g plain flour
pinch of salt
1 tsp vanilla extract
150g Victoria blackberries

1. Begin by melting the butter in a heavy-bottomed saucepan over a medium heat. Once the butter has melted, you will need to stir constantly with a balloon whisk, keeping the butter moving so that the solid fats are not able to separate and burn. Continue to heat in the pan until the colour changes from golden yellow to a light brown. A nutty smell will let you know that the butter is ready. Immediately pour from the saucepan into a separate bowl to rest. If you leave the butter in the hot saucepan, it will continue to burn.
2. Add the 35% white chocolate to the bowl of warm butter and allow the chocolate to melt in its residual heat. This higher cocoa content is less likely to split or cause any trouble!
3. In a separate bowl, beat the sugar and eggs until pale and thick.
4. Add flour and salt to the pale mixture and combine gently.
5. Ensure that the white chocolate has melted completely and stir into a thick liquid with the melted butter. Stir this into the blondie mix along with vanilla extract.
6. Slice the Victoria Blackberries in half and gently fold the into the blondie mixture ensuring that they are evenly distributed. If one or two of the berries break and release their purple dye into the mixture, well that is just fine.
7. Pour the blondie mixture into a prepared brownie tin and bake for 35-40 minutes, until set and crackled on top. Allow to cool completely in the tin before slicing into generous slabs.